What are you calling flutter? When your plane is sitting in front of you on the ground, do the ailerons have play (capable of movement without the servo arm moving)?

Are you using clevis's or z-bends? Are the clevis's snug to the pushrod? some clevis's are slightly larger than the pushrod, and therefore have a bit of slop.

Which servo are you using? How long is the servo arm as compared to the horn attached to the surface? The horn and the arm should be approximately the same length.

That's all I can think of....