Even after sealing the Dyna muffler with a tin can crush seal I still couldn't get it to completely seal. I was still having small leaks. After many tries I went and found a better method.

Go to the auto parts store and buy some tiger patch for exhaust. It comes in a few foot long strip. Cut the whole thing in half and get yourself a pair of scissors and cut one half down the middle long ways. Unbolt your clamp and slide it up the pipe a ways so you have some room to work. Wrap the whole thing with your 2 thin strips and make sure you pull it tight and overlap. You may have to hit the sides of it with a lighter or torch to get it to stay wrapped. Slide your clamp over top and clamp it down. Then take the rest of the fatter part and wrap it criss cross around the clamp. Start your engine and let it run a few min to melt it all together. If you have to remove it later it comes off easily with a razor blade. Enjoy your new completely sealed exhaust!!!!

and it'll burn thru too soon

best seal is welding that pregnant dog on :-D