I use pull-pull on most of my planes, big and small. I have found that I leave the lines as loose as possible, just enough tension to keep them from saging or jumping off a pulley when I use a pulley. You may have some reverse Ackerman (a term that is occasionally used to describe the offset of the attach points relative to the hinge center line). I usually deliberately put in a little Ackerman so that the cable not being pulled goes slightly slack when the other cable is pulled off center yet have both cables just snug when the surface is centered. I do this by having the attach points at the horn on the surface a very slight distance behind or aft of the hinge center line. It can be done at the servo side also by having the attach points slightly ahead of the pivot on the servo arm. In any case, make sure that the surfaces move freely when the control lines are not connected, i.e. free and all hinge lines on a straight line with no friction.