Here's a thought... when u originally balanced you model, was it nose heavy or tail heavy? if it was tail heavy, where did you mount the weight to balance it?

Reason i'm asking, i learned about a guy who balanced his full scale plane with a bowling ball in the tail area of the plane. Even though his plane ended up within CG limits, when he put it in a flat spin, the centrifugal force of the weight being so far towards the tail put him in a flat spin that he ended up crashing from.