Coming from a beginner that flies a Eagle 63 trainer w/ .40 2stroke:

For what it's worth, I just performed my first knife edge last Sunday. It takes a lot of Aileron/Elev to move the plane in position, all the rudder you can muster by moving the pushrod to it appropriate holes, about 50% aileron to counteract the dihedral wing trying to right itself and a fair amount of elevator to keep it from sliding in circles. Oh, did I mention WOT?

But that's on mine. Start with a lot of altitude cause she comes out of the sky pretty quick. As mentioned by someone else, the fuse doesn't provide much lift so your engine needs to be big to hold altitude. Mine was about 15seconds and I lost about 100ft altitude in the manuever.

It's takes a lot of intense concentration on my trainer. Good luck!