Don,

Tighten the bolts till they are snug. Use a little loctite on the bolts and that will keep them from backing off. You don't need to tighten them so much to distort the metal.

It should be fine as far as mounting unless you have a vibration issue. If you want to add a bracket for support I suggest you drill and tap the far end (oppisite the mounting bolts) in the direct center of the canister. Use a small bolt and again some loctite, a peice of rubber or silicon may also help with vibration. Again if you are going to use a bracket for support it will need to go to the engine or engine mounting bolts so that it moves with the engine. If you attach it to the fuselage it probably will break as it will not allow the muffler to move with the engine.

Al Young
JTEC