If you have a control (rudder) that takes 40 oz of torque to move to full deflection at 70 miles/hr it will require a lot more to move the same rudder at 120 MPH. Airplane speed, amount of deflection, surface area all come into play when deciding on the power required. And as Mike said, you can also strip plastic gears after a limit is reached. At that point flutter sets in and you no longer have to worry about it because you may no longer have a plane. [:@]