Check all your control surfaces closely - make sure the hinges aren't worn/damaged. Sky Raiders before the pinched nose had pinned hinges that could wear, the pinched nose versions have CA hinges. Also check your aileron torque rod's for any movement. I had to cut into the bottom of the TE and glue mine back in, and the routing the TE block was way too large for them allowing for forward/aft movement of the torque rod. Also make sure your servo's don't have any slop in them. We race Sky Raiders with the .46 AX and routinely dive them full throttle vertically with no flutter issues.

Hogflyer