the reason it comes off easily on there is coz people over the years have used back to black or other products with silicone in them on the black bits wich makes it hard for the vinyl glue to stick to.
giving them a good scrub with thinners then once pinstripe is on run a heat gun over it helps.
id did all this to mine but it still came off after a wile.
if people have used silicone products on it it may be hard for paint to go on nice aswell.