Having used pull-pull on many large models as well as some small ones, I have found that two things lead to a successful pull-pull system. 1: have a slight bit of positive Ackerman built into the system (this is where the cable not being pulled will get slightly slack as the other cable is pulled off neutral and 2: just enough tension to keep any sag out of the line, keep it as loose as you can. I use pull-pull on both elevator and rudder as it is so much simpler, lighter and more reliable than push rods. It also makes split elevator hook up easier.