Check the output menu page #1 and see what you're sending to the output in use.
For example: If you use Monitor Out to your power amp and you have DLY/REV Wet selected, you'll only hear the sound from these 2 slots (DLY and REV). If these are switched off, you'll hear no sound at all. Use Master mono instead
While overdrives were originally designed for "overdriving", in the high gain metal and Djent world overdrives are mainly used for shaping and tightening the sound
Thanks for chiming in again and I totally get what you state. But ...
1. Have you noticed that you didn't mention e.g. Bluesrock, Rock at all in your post? Where's all this stuff? Joe Bonamassa? Warren Haynes? Matt Schofield? Jeff Beck? Just to name a few Klon users. Or what about David Gilmour and the Colorsound Power Boost which often is considered the first overdrive, with ridiculous headroom and crazy boost to get a HiWatt to sing? No factory presets that fall in this category at all? C'mon 
2. Tell me which metal/djent player uses a Klon to "shape and tighten" his sound ... well, I just had to write this off my chest, hehe
If you state that there's "more to it than pushing an amp", this basically means there's some stuff beyond it's original purpose. Maybe you should at least add a few presets that take this into account (or change the Klon presets for what this pedal is supposed to do and most likely will be used for, at least by the guitar heros). 
They can't use their ears and are in need of a frequency graph in which to guide their enjoyment.
I like your sarcasm 
But let me tell you in all seriousness that I always use my ears first ... always. And only after I hear something I try to figure out what's going on, e.g. by doing comparisons/measurements. I guess it's part of an audio engineer's job description to be able to hear, compare, check.
Now, what would happen if I posted audio examples/demos? First of all I would get ripped apart because I'm not a decent guitar player. Then all the sceptics would still "hear" differences where there are none. We all know this game in the internets.
All I can do is try to show and explain ... and then each and everyone is welcome to just do their own real world comparisons and checks.
Now back to the Blues Brothers' Rawhide scene
1 - Ceriatone in front of the KPA input rather than in a loop?
I confess I didn't try for 2 reasons:
1. I was too lazy to plug/unplug the Centura for the measurements because 2. the Centura (like the Klon Centaur) doesn't have true bypass. Even when switched off, the signal still runs through the input buffer and 2 (irrelevant) high-pass filters.
Let's see, if I'm not tired of this testing I might try this tomorrow, just to make sure.
2 - Loop Distortion instead of Loop Mono? I don’t expect any difference in this instance as the change is really the way they behave on input rather than output.
Exactly. Since I have nothing in front of the Loop Mono, it couldn't have messed up the gain staging anyway.
3 - adjustments to Loop Volume. Is there any possibility that the Loop level is actually slightly boosted compared to unity gain? I know you are well versed in gain staging so I assume you have already thought of this but thought it might be worth double checking just in case.
Good thinking here! But of course I made sure the Loop Mono volume is at <0.0>
When I turn it down by 2.8dB (volume setting -1.3) with the intention to match the Kemper Drive from this side, the result is (not so) surprising:
The actual peak level rises by 2.4dB ... the opposite of what we would expect at first glance. The reason is that turning down the return signal lessens the amp compression. Again, it's also quite audible ... and not a solution to the Kemper Drive volume diff anyway.
The thing you call a distortion graph doesn't look like a distortion graph
Fun fact: While it might not "look like" to you, it actually IS a distortion graph, it shows the complete distortion component. But I'm sure you could have come to this conclusion on your own.
But if you're not interested in a discussion, OK.
I'm interested in a discussion of the topic "Kemper Drive", not in a meta-discussion about trust or distrust. If you don't trust, just move on. You already have access to the data via the graphs I posted. The data sets won't give you any further relevant information. Do your own if you need. You can't use mine for comparison because you don't have my profiles, you don't have the Ceriatone Centura.
Regarding the distortion graph, I ask you: How relevant would THD be? Do you think it would be very relevant to just look at the total harmonic distortion? Or is it more helpful to look at the complete distortion component?
REW doesn't allow for multiple distortion curves on one plot, so what are you showing here?
The art of Photoshop's editing capabilities and layer modes (in this case "Lighter Color") That's why I initially didn't post these distortion graphs, I was just too lazy to fire up Photoshop to color/merge/overlay the separate graphs.
Regarding the data set files ... if you don't trust me, say it openly. Otherwise, why don't you do your own tests (and findings) if you know the tools?
First off, let me say thank you for setting up and doing these measurements in such a scientific manner.
You're welcome ... and rest assured that it's interesting to me as well. So much easier to actually learn and understand (in this case the Kemper Drive and how it behaves).
If there is a change in output needed to reach the exact curve
I think the issue is slightly more complicated and probably beyond what I know and understand. Let me explain:
1. If I use my actual Centura via Loop Mono, an increase in pedal "Output" doesn't change the overall rig volume. It just compresses the amp harder and lowers treble and boosts bass. So far so good, I can understand that.
2. When I use a Pure Boost (after the Kemper Drive with volume at +5.0) it doesn't do a thing, even at +5.0. No additional compression, no volume boost, nothing.
3. These findings plus the fact that I don't want any additional amp compression tells me that I have to increase the volume in the amp block by 2.8dB if this volume diff is important to me. 2.8dB can be heard but when you disengage the Kemper Drive you don't necessarily want these extra 2.8dB.
Weird situation, to be honest. And I think it has to do with the internal gain staging of the Profiler (Kemper Drive vs. Loop Mono).
Zieh mal für ein paar Sekunden das USB Kabel ab ... dann wieder dran.
Ich vermute mal, dass deine Namensänderung nicht "im laufenden Betrieb" mit dem Rig Manager synchronisiert.
Curious, what would be the unity volume setting for centura with such gain setting?
Not completely sure what you mean.
But if you mean where the Output knob of the Centura must be set to not add boost, it would be roughly 7:30 o'clock (but it obviously depends on the Gain setting as well). It's pretty much the same on the original Klon Centaur.
it really isn’t possible to get the control knobs into the exact same position to do the comparisons.
Let's try to play the opposite game, ok?
You find me a well-known guitarist that uses the (original) Klon and show me if they have set their Output knob to not boost the amp. It actually doesn't matter if they play bluesy, crunchy tones or singing lead sounds with an already distorted amp.
To help you a little, this would mean the Output knob on their Klon would have to be set to 7:30 o'clock. Why? Because anything beyond 7:30 o'clock (or let's say 8 o'clock for pot taper tolerances) would definitely require the Kemper Drive's Volume increased for a perfect match. Simple as that.
Proclaiming none of the presets do justice to any of the original pedals without comparing any of the presets to the original pedals might be a bit of an over-generalization.
I was referring to typical applications. I'll give you a real world example, ok?
Joe Bonamassa had a Klon in his rig that fed one of his Silver Jubilees. I know the exact settings of his Klon and also of his Silver Jubilee. Let's just start with the important part, the Klon. His settings were ... Gain: noon, Treble: 11:30 o'clock, Output: 11 o'clock
I can tell you for sure that (with the Silver Jubilee profiled according to his settings), it's absolutely impossible to match his sound without pushing the amp (aka increasing the Volume parameter of the Kemper Drive).
I don't think anybody on this planet would accuse Joe Bonamassa to use a Klon wrong. I would even go as far as saying ... if there ever has been a "sweet spot" on a Klon, Joe would likely use it. 
And it's really easy, even for a beginner, to hear the difference immediately. The added push into further compression adds a lot of sustain, makes the treble smoother and the overall sound just a beautiful singing lead tone.
One more run regarding my Ceriatone Centura, this time with another amp. First the details:
Marshall Silver Jubilee JCM 25/50 Model 2555
Lead Channel OFF
Presence: 10
Bass: 9
Middle: 0
Treble: 10
Output Master: 10
Input Gain: 7
Profiled with Tube Thomsen 4x12 cab with (british) Celestion V30s using Shure SM57 & Beyerdynamic M160
Resulting Profile:
Amp Gain: 3.0
The amp is setup to be pretty clean, just barely at the edge of breakup.
Now the Ceriatone Centura joins the game. I have it setup like this:
Red Lines:
Gain: 1 o'clock
Treble: noon
Output: 1 o'clock
Result: Quite crunchy sound, not as dynamic as the JCM 800 Bass Series I had used before, doesn't clean up as easy with lighter picking.
And finally we look at how to replicate that sound with the Kemper Drive:
Dark green lines:
Drive: 4.0
Tone: 5.0
Definition: 5.2
Slim Down: 0.0
Volume: 0.0
Light green lines:
Drive: 4.0
Tone: 5.0
Definition: 5.2
Slim Down: 0.0
Volume: 5.0
Frequency Response Graph:
Distortion Graph:
As you can easily see (and I can easily hear), again the Kemper Drive's Volume makes the difference, significantly. I don't know why the Volume isn't taken into account in any of the Kemper Drive presets. The Full OC presets make use of it. None of the Klon presets makes any sense (to me) and I'm baffled as to how this can be called "sweet spots". I don't have any of the other overdrive pedals emulated in presets, so I can't compare them. But I highly doubt they get close to what their real counterparts are typically used for!?
My personal bottomline:
Kemper Drive CAN be really great but the provided presets don't do their real counterparts justice, sorry.
have you tried an intermediate setting, especially considering that the low/sub bass frequencies are of less importance anyway?
Not yet but I will do a bit later. But keep in mind that you refer to the distortion graph, not the frequency response graph I had posted earlier. An increased distortion in the low/sub bass frequencies adds harmonic content to the overall sound. You can actually see that (and I can easily hear it) in the linked frequency response graph. From around 400Hz downwards the curve goes up when you compare Klon 4 (default) with Klon 4 (volume +5.0)
PS: All this (to me) makes the beauty of the Klon (or good Klon clones). The warmth they add when you use it to push an amp. That's exactly what distinguishes it from say a typical Tubescreamer application. I love this "scooped" sound as opposed to the pretty heavy mid bump and low cut of a typical Tubescreamer sound.
PPS: I tried Klon 4 with Volume at 2.5 ... it has a slightly higher bass frequency response but at the same time (as expected) the low frequency distortion is only half way between Volume 0 and Volume 5 ... leading to a slightly less scooped sound. Nice sound as well with a slightly higher overall volume but not as close of a (sound) match like with Volume at 5.
So is it a case of increasing the drive pedal volumes actually changes the sound characteristic? i always assumed the kemper volumes just added the volume with the same sound
It's not the drive pedal alone ... that's why you can't see the effect without an amp and a cab loaded (and active). The entire drive pedal (all of its knobs) have an effect on how the amp (and cab) reacts. You basically drive the amp into compression. The compression of the amp changes when you "overdrive" it with increasing input. And this results in a change of sound (not just pure volume, not just linear increase of distortion).
There is more purposes for an overdrive than pushing an amp.
While they could be used for other purposes, their main application right from the start and the reason to create them was to do exactly that, push an amp. The name "overdrive" actually says it. Maybe you want to read about it from another person than me? Here you go:
https://www.gilmourish.com/?page_id=7748
I know that it's quite hard to convince you of something (which isn't necessarily a bad thing). But I just demonstrated it to you, in my earlier posts. The classic application of an overdrive in combination with a relatively clean amp with plenty of headrom ... similar to what the Hiwatt Custom 100 does. The Marshall JCM 800 Bass Series is quite similar in this regard.
... ya'll could have recorded a hit single that sounds great. Just sayin'. 🤣
I'm not in a rush, publish yours first
And here's the distortion graph, same color code as the previous one:
Red Line: Ceriatone Centura
Dark Green Line: Kemper Drive Klon 4 preset (default)
Light Green Line: Kemper Drive Klon 4 with Volume +5.0
See how extremely close both are with Volume set to +5.0? Just again these 2.8dB missing for a perfect match between 35Hz and 11kHz.
And again it's interesting to see how the Volume parameter of the Kemper Drive affects the bass response up to roughly 120-150Hz.
PS: Just for the record ... I did the sine sweep for all measurements with -15dB which is close enough to the average level I get when I strum my Gibson Les Paul medium hard.
So the bass curve changed that much from just raising the volume?! And this graph is of the stomp only or it includes the profile?
Yes, just by raising the volume. The graphs are with the profile, of course.
Why do you wonder that the sound with KD is thin, when you have not treated the Volume at all, as you did on your Centura?
Well, probably because I thought that the preset is supposed to act like an overdrive pushing an amp into a nice crunch?
But I (almost) got it done ... remains the question about the missing 2.8dB to make it a 100% perfect match. It's audible and it's also visible in my screenshot (red line vs. light green line).
