[TManiaci]

CF Rods work well too, anything that presents a solid straight line and minimal droop. The pair of rods should droop the same if they are equal. To mitigate gravity, you can roll it over on it's side and look down, but on a 40% you need a ladder, LOL.

This method is particularly useful in the case of ganged servos. When you have two servos on each elevator half, tuning out the binding of a pair of one half always changes the surface angle a little, which then requires going back and resetting center and endpoints again. It's a process of iteration to get it right.

In this install, I have two pairs of Futaba S9156. I can see a slight repeatabillity error with this rig. The Futaba's don't hit the exact same spot every time, and if you wiggle the stick, they get back together. When you can see the servo resolution, you know you are getting down to the nitty-gritty precision the system is capable of.