Quoted from herg:How would we test how well this worked? Waxed paper?
Interesting experiment and nice work. I think the next step is to use the real deal, vinyl decals. Someone has to have a decal they screwed up that could be cut up for testing purposes.
Either way I've always used this stuff:
http://303products.com/index.php/303r-aerospace-protectant.html
You can tell if it is still working by touch--feels a bit like wax or SPF lotion.