No, those will not work at all. You need a proper prop hub. Remember, safety?
Yes, get the muffler clamped in a vise and use a flat head screwdriver to start that crimp coming undone. The hardest part is getting it started. Once you start raising the crimp, it is easy to work your way around a little at a time and get it bent up enough to get the muffler apart.
AV8TOR