NFOOTE
Thanks for the input.
As you work at Boeing on flight controls you should be able to find somebody who really knows about Flutter and mass balancing. As you know, the 747, 757, 767 and 777 do not have mass balance. Their controls are hydraulic. However, the hydraulic controls on the 737 had manual back up, operated by cables, and it had mass balances. Ask somebody what the mass balances were for. Ask what happens when a mass balance falls off.!!! I am sure I once read a safety report about that. Incidentally the 737 ailerons also have internal aerodynamic balance.

From my standpoint Rodney is still quite wrong. He contradicts not only my model flying experience but also every aerodynamics book that I have read on the subject of flutter.

Maybe it is a language thing. Maybe in the USA you can use the term Aerodynamic Flutter for any bit of aeroplane that wobbles around a bit. But in my Degree course in Aeronautics it was very specific.
Aerodynamic Flutter is a driven vibration. It depends on the masses and stiffness of the wing and ailerons etc and the displacement of the masses from the flexural axes and it also depends on AIRSPEED, which is the term Rodney has omitted. I remember (from many years ago) that the analysis evaluated the work done by the forces in the system as a function of airspeed.
The result was that above a certain airspeed the net work done was positive, that is , energy was extracted from the airflow and so the flutter was self perpetuating. Below the flutter speed it was damped out.

What Rodney seems to be concerned with is Resonant Vibration. That too depends on masses, stifness and some form of stimulus. He has not mentioned airspeed. If airspeed is not involved it is NOT FLUTTER.
Alasdair