Hi ive got a black horse models chipmunk and im having problems balancing the plane. I have got an os 70 ultimate four stroke engine in the plane. The balance point by the manual is 100mm from the leading edge of the wing. when i tried this the plane was so tail heavy i couldent get the tail off even with the battery and all my gear as far forward as i can get. i tried 8 oz of lead and still cant get the weight forward. Any sugestions would be gratefull