The only plane I ever owned where I experienced flutter was a Carl Goldberg Anniversary Cub. It had a full wing and strip ailerons. I had a Magnum .61 XL under the hood and it was FAST!!! I really miss that airplane. I sold it to a friend because I thought I had "moved on." I'd like to "move back" now. I didn't realize how much fun that airplane really was. It was my 2nd airplane build and I had the horizontal stab glued on with an angle, not glued on perpendicular to the airframe. It was repairable.

The trailing edge of the ailerons were squared.

It turned out, once I sealed the hinge gap- I never had flutter problems again.

Just a thought...