And i decided to test out the targets and as you can see the only liquid that didn't remove the art was water.

Water didn't damage it at all
Windex worked ok if used very lightly but it did smudge
Metho as expected just ate it right off
Novus 2 as with windex if used very lightly might have been ok but did smudge

So clean them at your own risk

 I hope this helps a few people to have a go at repairing there drop targets