how to shave the gas cap on my demon

Off the top of my head...No. I had a rental car last year with one. Don't remember what. Just something they gave me at the airport.

Push to release, push to close. As long as the quarter is less convex than the Demon should be really easy. I'd cut a foot all around it to give plenty of room to blend it in. And of course take as much of the neck as possible.
Ok. thanks.