[caldrail]

Well from what i see, the fuel tank issue doesn't really effect the mustang. So i cannot make the Aft tank drain first, but i do not think it would make a difference the way the game FM is modelled.

Correct, Il2 doesn't model the CG shift for the FM - it only calculates the _weight_ changes.

Actually it does model CG shift. When you put flaps and/or gear down, it has a value for CG shift.

CG shift? For lowering wheels and flaps? What for? The most important CG change is longitudinal and these circumstances don't affect it. Lowering all the dangly bits does affect drag however so perhaps the values are simply there to model trim changes by another route?