At the 2003 Worlds, I had one plane (same design) with 9650's and the other with 9151's on ailerons. The 9151 plane snapped better than the 9650 plane. The 9650's worked, but it took "a while" to get the snap going. The 9151 was an instant snap. So there is a point where too little torque is reached, at least for snapping maneuvers. Rolls were fine as long as there isn't too much speed to blow back the surface. I'd say up to Advanced, no problems.