i can't imagine that you could fly inverted (outside loop) but you can't do a aileron roll... am i missing something? when you are inverted preparing to go an outside loop, you will need to roll and fly inverted. according to your claims, once you get halfway through (inverted by then) you go straight down!!!

anyway, i'd agree that you should try to get a shallow climb and try the roll without any elevator input. i'd also maybe add some deflection on the ailerons.

now i'm going to ask something stupid ... you have ailerons, right? i mean a lot of high dihedral trainers can be 3 channel planes.