James,

Just a semantic note -- if you're seeing it vibrate on the ground, I wouldn't call it "flutter" as understood by aeronautical types. What you're seeing is slop, flex, or some kind of harmonic vibration. It will surely lead to true aerodynamic flutter in the air, but it isn't really "flutter" yet.

You did the right thing by replacing the aileron with a piece of stiffer wood. Other than that, sealing the hinge gap with tape is the next best thing you can do to prevent flutter in the air, whether or not you see it wiggling on the ground. This will also increase the effectiveness of the control surface. On one of my sport planes I just about doubled the roll rate by sealing the aileron hinge gap. For racing this means you can cut down the throw (control surface travel), which reduces drag, which in turn results in more speed.

Speed is good.

DHG