Found it, this is a photo of a high wing trainer using a single servo that has mechanically induced differential. Note the pushrod holes in the round arm are forward of the output bushing of the servo.

Note I do not reccomend the use of EZ-adjustors on these pushrods as in the photo I much prefer a 'Z' bend on these rods and a clevis on the other end at the aileron torque rod horns.


John