I assume that the Avistar uses a single aileron servo and torque rods?

Hooking the pushrod closer to the end of the servo horn will give you more through since the tip of the horn travels farther than the area closer to the center as it rotates.

Also, putting the other end of the pushrod closer to the wing (pivot point of the torque rods) will increase throw.

To lower the throw, just do the opposite.

The trick is to find just the right combination to get the throw you want. Even with computer radios, you want to try and get everything as close as you can mechanically before making adjustments electronically in the radio.