Are you using 8520? We overlay on it a lot without issues... If its flat, or semi curved you'll be ok. If you're going into a big recess... it doesnt hurt to primer it.
Heck... if you know where the strip is going, you can use Masking / knifeless tape and then primer everywhere the stripe will be, go overtop of it... remove the masking / use knifeless if thats how you're doing the stripe, and it'll pull both vinyls off before the gloss would lift.