Put shell holes in wrong place...

[sosidge]

For some reason I've managed to put the bodyshell holes a few mm away from where they should be (despite measuring twice and cutting once )

I've reamed out the holes a bit bigger to correct, but now obviously I have an oversized hole.

Any suggestions on a way of backing up the hole with a bit of extra material to stop the shell moving around too much?

In the past I have used the self-adhesive foam body washers, but don't have any to hand. I was thinking of making a washer with scrap lexan, but what should I use to bond it to the shell without damaging the paint surface or looking too obvious?