With three servos located in the tail, the 16 oz. fuel tank centered on the CG, and the 5 cell 1700 mAh battery right behind the fuel tank, it needed some tail weight to balance. The engine swings a Zinger 18 x 8 wood prop at 7200 RPM (still breaking it in) and hauls this 17 lb moose around nicely. It will cruise around at half throttle (around 6000 RPM) and climb out with authority at full power.