One potential benefit of this system would be that you lose the nonlinearity associated with our current arm/pushrod/horn setups. With zero expo on a direct drive system, the surface should move exactly linearly (at least as linearly as the servo being used). Most people would probably still use some expo, but if nothing else it may make it easier to compare expo values between setups which may have different length pushrods, servo arms, control horns, and different control horn locations relative to the servo.

Baron