Mass Balances do work and I have never found a case where they would not regardless of power or velocitys. Mass balances simply move the onset of flutter beyond any speed the airplane is capable of ever reaching at any power or dive angle.

I was in the habit of making up bunchs of them to take to the old SWRA warbird races Here in the southwest and later in RC Pro warbird races. Flutter issues were/are common at these events and in most cases it tended to be the ailerons, especially with strip ailerons.

When one of the fellows survived an episode of severe flutter (meaning extremely obvious) I just shared a pair and all he needed to do was go poke a hole in his ailerons and he was good to go for his remaining rounds, works every time.

John