ORIGINAL: goirish
i think one thing you should try to achieve is to have the control horns and the servo control arm the same distance . For ex., 3'' servo control arm=3'' on the control arms. That way every thing moves as one unit. If MinnFlyer is around he will post a picture of what I am talking about.
If you follow Rodney's comments regarding where the control horn holes are in relationship to the hinge line - you are good to go. The servo arms don't have to be the same length as the control horns unless you want a one to one ratio of movement - just like you would do with a standard pushrod setup.
We have been hammering this out over in the "Questions and Answers" section under the "Pull/pull wire crossing" thread. More than you would probably ever want to know!
Kurt