Thank you for your quick responses. A friend of mine was wondering if it was possible to do a pull-pull on the rudder and elevator of a Piper Cub kit he was planning on purchasing.
by Campgems:
"but it requires a bit of geometry to make it work well.The basic idea is to translate the movement of one end of the servo arm to an equal movement of the rudder or elevator horn. This requires a couple things. First, the center of the servo arm to the attachment point has to be the same as the hinge line to horn attachment point. 1/4 " of movement on the servo arm attachment point has to equal 1/4" of movement on the horn. If you don't have this setup correct, one side of the cable is going to go slack. This results in fluttering some times.
The second thing is not to build any Ackermond (spelling??) into the linkage. This requires that the center of rotation of the servo and it attachment points or both sides be on a single line, and the same goes for the control surface. Right horn attachment point through hinge line to the Left hor attachmen are all on one line. This ensures that the control surface exactly follows the servo movement and that both cables remain tight throughout the move. "
According to the above detailed explaination it would be way beyond mine or my friend's understanding or abilities.