I have allen bolts in my triples on 2 450s and I haven't had any problems with them backing out or snapping. Both of these machines have a lot of races and wrecks on them, it's not anything you need to worry about. You could file them flat where they make contact if you have the room to spare, that will help with the chipping. But all stops are metal to metal contact, you're going to get chipping no matter what if you slam them.
Looking for a Bassani silencer for a 2nd gen tecate, the style with the movable mount. 1st gen will work