No, I meant the control "arm" on the servo itself. I'm sorry I said control "horn." I also forgot about the Avistar using only one servo so the method I suggested will NOT will not work. For this, I apologize! It DOES work when one servo is controling one flight surface however. It is possible to move the control arm forward or backward a notch on the servo itself to get more throw either up or down.

In your case I would consider turning the clevis's in a few turns so you do have more up throw than down and cranking down the horns on the torque rods a few turns so you have more throw overall. Don't crank the clevis's in so much that your ailerons act like spoilers however. If you do you will lose lift.

Again, sorry for creating confusion blueangel.