In reply to Woketman, c/f and mr_matt

Regarding flutter:

Flutter is caused by an aero dynamical effect with a flutter frequency depending of the speed of the aircraft.

When this flutter frequency is the same (or very close) to the natural frequency of the control surface system then the flutter amplitude is amplified and the acceleration and forces in to the system will also be amplified. This is typical for a bad case of flutter.

A very rigid linkage and slope free servo transmission will contribute to a high natural frequency of the control surface system.
When you mass balance your control surface you also contribute to a high natural frequency.

Ideally you want a natural frequency of your control surfaces which are way above the aero dynamical flutter frequency at maximum flying speed.

Regarding torsional flutter of the elevators I think you can rule that out quickly by twisting an elevator half in your hand. Then compare the stiffness with the “system”. It should be quite obvious that the torsional stiffness of the elevator is significantly higher compared to the stiffness of the system.

Please correct me if I'm wrong.
/Johan Tinde