The counter weight or BALANCE is the way.

My understanding is that every airplane (yes full scale too) has a 'flutter' speed __ period.
Get to that speed and you've got flutter.

Over the years I have had 'flutter' remove ailerons, aileron servos (yep, the whole thing) etc. but it has been a very sparce occurence. Perhaps three aircraft out of roughly fifty year's worth.
The elevator on a P-38 Lightning is the most visible "flutter band-aid" I can think of at the moment.
http://upload.wikimedia.org/wikipedi...tning_USAF.JPG

Most models, including my few that had a flutter were overcome (it's a 'fix' not a cure) by your #1. Incidentally, it can work with the reflex either + or -.
I cannot buy your reason for not trying it. I have simply never experienced that which you have stated as a reason not to. I have used refexed airfoils for a variety of reasons, flutter is but one.
I also do not agree with removing the outer portion (6.5" you stated). Removing the whole aileron will stop the flutter too. Need I say more?

I am NOT an aerodynamcist, but we have several on these threads who are.
Hopefully they will chime in