The two most common mistakes that cause people to complain about their pull-pull systems is 1: No positive Akerman and 2: to much tension in the lines at neutral position. For those of you who do not know about Akerman, there is a wealth of information on it on many of the RC forums (use the search feature) or just Google "Ackerman" and sort through those sites related to RC. It's not complicated and can be the difference between a smooth well working pull-pull system and one which eats up battery life and wears out servos.