Yep, control surface flutter can be real problem when trying to get speed out of a 3D plane. To save on weight and lower wing loading sometimes too many shortcuts were employed. Todays composite 3D planes can handle more speed than just a few years ago.

I've seen two Cadet Sr's turn into balsa clouds in the last few years. Both exploded on full throttle down lines in a loop. Both were ARFs, both had 55ax 2 strokes and both had pilots that over estimated the strength of the airframe. The wings are prone to flutter when pushed too hard.

I've not run a 65 or even seen one run in person. I do love the power to weight ratio of the 62 though. Crunchy has one of my fa62 rebuilds, I look forward to hearing his reaction when he test runs it. Last time I tested it produced 1.07 hp spinning an apc 12x6 at 10100 rpm. Very strong runner. Not as smooth as a 56 but not bad on vibes.