As one who uses pull-pull on nearly all my planes, on both rudder and elevator, I have found that you always want some positive Ackerman in any pull-pull. If you do not know what Ackerman is, just google for it as there is a lot of good info available . Basically, it is adjusting the attachment points relative to the hinge point so that the line NOT being pulled on always goes a bit slack as you move the surface away from neutral. The trouble most people get into on their first pull-pull is to get some negative Ackerman built in and that can cause all kinds of problems as it causes excessive current drain on the servos as well as possibly causing binding and/or restriction on amount of throw.