as another point of view, if it's truly high speed flutter, I seriously doubt that your "weak" servos are causing the problem, unless the out put gear is now stripped and missing some teeth..... even if the servo can't hold the aileron perfectly still, the torque applied will dampen the oscillations dramatically and reduce the frequency considerably.... no, I would bet your problem is loose, inadequately sized, or poorly installed linkages or bad hinges or big gaps or some other mechanical phenomenon....

[:-]