The 1.08 is inverted and I lowered the tank to avoid problems. I run a sportscale muffler which is like a set of straight pipes out the bottom. A 91fx will definitely bring scale flight. Honestly I think you could use some more power than that. Its a nice flying plane. many guys have them here and all a happy with them.

Honestly I don't think your going to get the performance you want with a 91fx with good loops and vertical but that is only my opinion but it is a nice plane