I just looked at the plans and they call for a 45 to 61 two stroke so the 91FX should have plenty of power.
I don't see where a 45 motor would near enough.
The box says it should weigh 6 3/4 to 7 1/2 lbs, I have the wing 90% done and the fuse 75% done with the tail feathers on and six of the seven servos and mine weighs 2 lbs 7 oz so far. I still have 2lbs of sanding to do yet.
DEG