Leaving headroom in a recording only applies to an analog recording setup. Lowering a digital signal by 12 dB will reduce the resolution by two bits from 24 to 22 but will not prevent any clipping since you cannot clip a digital signal by definition.
You can use the channel fader in your DAW afterward to set the desired level in the mix. The DAW usually works at a much higher bit resolution and uses floating point.
turning down the fader before or during the recording will make no difference. Try lowering it after you have recorded the signal. That should surely attenuate the signal.
I suspect we are talking about monitoring the signal during recording? The DAW fader won't do anything unless you monitor through the DAW which you most likely shouldn't here.
There must be a volume control in the Kemper to control direct monitoring volume, and I'm pretty sure rig volume isn't the right one 
The Kemper defaults to Direct Monitoring every time you restart. I suspect the reason the fader makes no difference is that you are hearing the direct sound of the KPA rather than input monitoring through the DAW
Thanks to everyone. It’s making sense now. I need to record what the profiler gives you, then use the faders to adjust db.
I think I was making it too complicated. 
