I have a modified a Gremlin by adding a coroplast tail assembly. I have a Magnum .28 on it and it flies great. I flew it a few times until I broke in the engine and I then added a mousse can muffler and then went and flew. First of all, man,... that lil engine will really haul. But as I was doing a High Powered flyby. I heard the bbbrrrrrrrrrrpppppp............. sound of flutter. My question is how can I tell if the flutter is comming from the ailerons or elevator. The plane didnt bump up or down while fluttering so that would make me think that it could be the ailerons but that coroplast does flex. I will include a pic of the plane. Now I have trimmed the stab quite a bit with a good swept so that the only thing different from the pic. I was thinking of Trimming the outboard aileron tips at an angle appx 2 1/2 - 3inches inward to reduce any possible aileron flutter. My other option would be to build the tail assembly out of balsq but it would add unwanted weight. I just really wanted to stay with this design cause its alot more stable than a standard Gremlin and is more manuverable, in my opinion.

Thanks,
FUZZ