DesertRider49,

I mounted a 1500mAh 5cell battery on the side of the engine box and all was good in terms of balance. My understanding is that the newer versions have a wing tube that is aft a bit more making balance less of a problem with lighter engines. Remeber I had like the first on off the line (it's an exageration, but it was very very early). I would have actually used a smaller battery, but I needed a bit of weight and figured the oversized battery added flying time. Couple of suggestions - Only my opinion - I would only use metal geared servos, 100+ oz on the wings (preferrably more torque), also do not exceed a 8" pitch prop. Reinforce the mounting tabs in the wing with epoxy and glass so the tabs don't break loose. Oh another suggestion that you probably already know - use locktite on the servo screws when using metal geared servos...they will vibrate out otherwise.

Good luck,
Mike