I am using the OS 46 FX, a regular size JR receiver and servos, and I am way tail heavy to get even near the starting point of 3-3/8". I mounted the battery all the way foward up aganist the fuel tank wall, and the receiver is just in front of the wing hold down bolts, as the servo leads all reach to about there. The receiver does not weigh much anyway. Moving it won't make much difference at all. My CG is at 4-14" I followed the mounting instructions for the engine, but it appears so close to the firewall that getting the fuel line off will be a challenge. Question is, should I move the engine foward, and will that effect anything else?? Should I then put the battery in the center of where I have it mounted first, and then move engine? I figure if the battery is centered from the start, then you have the option to move it later if you like a different CG as time goes on. So the real question is, is 4-1/4' CG really bad, or will it fly like it is? Only problem is right now I am so tail heavy that I have nothing to adjust to get some weight in the nose. Any help would be appreciated. Thanks, and thanks for the last response as well.