HWM--Way to go, man!!!!
The muffler setup looks good. It should work in that position. I wouldn't worry about a vibration dampener between the engine and the muffler. The factory setup doesn't have one and neither do I. You really can't feel THAT much anyway.
Have the muffler guys weld an "L" shaped bracket on the back of the muffler so it can hang from the factory mount that attaches to the engine. You can then use the straps to secure the muffler in place so that it can be removed easily. The only welded portions should be the pipes that attach to the muffler.
The muffler strapping will work but looks kinda hokey(sorry,I know you are trying
)
Go to a tractor supply store/farm store and find the largest hose clamps they have. The width doesn't matter but I believe most are about .5.
You may have to connect 2 but I think you need about 18 inches diameter. I think they'll look better and less obtrusive.
Sorry about that. I got a little "wordy" but I hope this helps you out.