Hi, My Four star 120 with a 25cc toro suffered from flutter last week. I went straight up with it until it couldn't climb anymore, pulled the throttle down came straight down with it and both ailerons fluttered!! It sounds like the trailing edge of a kite flapping on a windy day. I lost control of both my ailerons. So I had to land with the rudder! Found out one servo stripped and the other servo mount broke loose from the aileron hatch. I was lucky to land it in one piece. I will now beef up the aileron hatch mount and use metal geared servos. Lesson learned!