The 91fs is pretty heavy for its power. As far as profiles go, the Mojo is a great plane but the 40 size is too small for the weight of the engine and the engine doesn't have enough nuts for the 60 to fly "right". Maybe a 65" yak from OMP but I think it'll be under powered. I'd dump the 91fs and get a 91 fx or another brand 4s like a saito or a ys.