I use saltwater fishing sinkers, and rubber cement. And I try to put it as far forward, and as close to dead center as I can. On my P47 (FMS 750MM) the weight is glued directly under the motor, and smack-dab in the middle, and it flies beautiful-like. C.G. is 55MM from leading edge on mine, and a tad nose-heavy with the battery in. LOVE this plane...