The ammount of torque for any control surface typically is determined by the size of the surface and the type of plane. The giant scale planes use hi torgue as the control surfaces are large and the planes are heavy. The 3D stuff has really large control surfaces and will use hi speed and Hi torque servos. The majority of the trainer planes use standard servo's. Hope this helps or if you have a specific plane that you are getting ready, let us know what you are building. Good Luck, Dave