Hi John
Don't weld a tab, clip etc. to the muffler as it will fatigue and break. Trust me I know and as an Aircraft Welder Tradesmen I understand why.
the best solution is to roll a strap of steel to fit the muffler diameter or to fit the tailpipe diameter, fold a small tab on this to bolt up to the chassis with a rubber exhaust pad between the brackets.
My first welded tab on my Birkin exhaust broke within a year, my repair as above has lasted 4 1/2 years and still going strong.
I have read posts in the past about rear exit tailpipes on 7s causing fumes in the cockpit but I have never experienced this on my rear exit exhaust. It certainly makes for a quieter cockpit on long drives.
cheers
Maurice