I just went through this with my GWS A-4, and the glider fanatic of my club advised me to put it 1-2 inches ahead of the CG. This allows the plane to rotate (as up elevator is applied and you throttle up) and fly off the bungee ring. So far it has worked fine. Kinda exciting watching your plane go from 0 to 60 mph in about 3 seconds!! CC