Giant Scale

AndySteere,
My 35% Giles has a similar setup with one servo on each elevator half and 2 servo's on the rudder. All servo's have the servo arms mounted upward. I have one of the elevator servo's reversed (using hitec digital servo's). Ideally you want the pushrod to be at a right angle to the arm and control surface. When setting a plane up for 3D and using 1.25" arms, the pushrods tend to run at an angle. The control horn is located closer to the surface, this allows the exaggerated throws necessary for 3D. I would reverse one of the servos and keep both arms upright. Set the pushrods up so that both side are equal. I tend to build some differential into the surface(not intentionally) because I am not perfect. If your hinge line is not perfectly centered or the control horn is not perfectly set into the surface, you will have some differential. Even if I use a drill press to drill my surfaces, I can never get them perfectly straight. You would probably need a lathe to achieve this level of accuracy. In any event, a computer radio can help to correct a small amount of differential. I try to get the linkages as equal as possible mechanically and then use the radio to fine tune the adjustment. I have not seen a setup like described in the manual but then again I have not seen every type of setup. Most planes that use tail mounted servo's use a reversed servo on one side of the elevator. Hope this helps.