My turn to contribute something towards the rig library.
I've uploaded my JCM800 merged profile which was done professionally in a Studio.
The profile was made using a tubescreamer and Boss GE7 in the chain (just to push the amp a bit)
I use Fishman Fluence modern pickups so you may need to knock the gain up a bit on the profile if needed.
I was amazed at how accurate this profile was to my amp when running it via a 4x12 (Mesa Boogie)
profile name - JCM800 Merged
I can upload the direct profile if anyone wants it.