@Rigel Kerman: I was playing around with the configs you created for RO, and I found 2 issues regarding CoM and angle keeping:
You have all the propellant in the aft tanks, but the real shuttle had tanks in the nose to serve the forward thrusters. By moving half the propellant from the aft tanks to the nose, the CoM now seems to be at the right place (about in the middle of the fuselage).
The RCS thrusters are way too weak. Based on the old "Component Space Shuttle" RO configs, I set the nose thruster power to 3, and the aft ones to 4, and that seems to work much better.
Also, not related to reentry, but I used the old "Component Space Shuttle" configs to correct some other things, like having CO2 scrubbers in the nose, and a proper fuel cell in the engine mount, with hydrolox propellant tanks.
Now the only remaining problem is the wings, which for some reason doesn't seem to be recognized by FAR. Upon reentry, the shuttle just turns to its side, and isn't able to turn back. I've tried different configs for FAR, but no luck
If anyone has any idea, I'm all ears, looks like this is the only remaining issue regarding reentry.