RE: a 13 pound plane with an os 91fx engine ?
I fly with a guy every weekend who flys a giant big stick with a 1.6 O.S. and it rips. I fly a .60 size big stick with a .90 super tiger and it rips. I'd say yours would be a good bit under powered,but it would fly if you have the proper runway and dont expect many manuevers or quick recoveries. Might actually be nice for landing it,just dont throttle back to far.