Gray Beard mentioned something that I am dealing with now. I have a combination of servos, some digital, some analog, and some analogs with higher torque, plus a few mini Hitec HS-81. My question is, where is the highest torque needed on a plane? The rudder, because of steering on the ground? Can I use an HS-81 for throttle without ball bearings or metal gears? Do ailerons require more torque/speed than elevator? I guess if we want to get scientific, it would have to depend on the airspeed, area of the control surface, and required response rate. But that is too much math for my simple mind.