If you added the lead behind the hingeline you just made things worse remove it immediately, but back to mass ballancing in a moment.

First assure that there is no damage as outlined by Jester to any of the structure, linkages and hinges. Next carefully inspect the servo and rotate them power off to full throws carefulling feeling for any stripped teeth from the flutter episodes.

Now if everything is solid (gap seals will not do anything to help) make four simple mass ballances as pictured, One for the bottom of each aileron. You do not have to ballance the surfaces completely or anywhere near it a simple thumb sized fishing weight will do about one and a half inchs forward of the hingeline.

This will stop the problem everytime unless there is now structural damage.

John