There are actually several things that you can do. Use the largest (physical ) battery that you can fit in the fuselage, and place it on the side that is lighter. Mount your receiver on that side too. If you normally use a 600 mah battery, you can use a sub-C pack and almost quadruple the weight of the battery, and you'd be surprised how much you can alter an out of balance problem. You get the added benefit of having around 2400 mah of battery power as well. If all else fails, you can add lead to the light wing tip, and a little does go a long way. Are you checking the balance by using the propshaft with the glow plug removed, and adding a straight pin at the tail to check the balance with?

Bill, AMA 4720
WACO Brotherhood #1