Monokote trim patches for covering holes - not recommended

A while back I posted that I had used Monokote trim to cover some of
the larger holes in my Speed Astir fuselage. They did a nice neat job
of covering the holes, but here's the follow-up. I removed one a
couple weeks ago that had been in place for a couple months. The
mylar pulled off cleanly, but left the adhesive behind, and boy howdy
was that stuff difficult to remove! Perhaps with the RIGHT solvent,
it wouldn't be a pain, but the 3M General Adhesive Cleaner doesn't do
much but make it gooey. If anybody knows what sort of solvent would
work better on the Monokote trim adhesive, please chime in, cause I'm
sure the 'racing checker' patches made my glider faster!