I used to just run the strap under the muffle and let it push it up a bit. Never had a problem. Might take a little pushing to get the muffler centered again, but that's like an extra minute of work. I don't use chains, I use straps. In the font I don't have the stock subframe so I I just loop through the wheel sand go straight out to the tie down. In the rear I cross. Never had a problem.
These are the straps I use:
http://www.summitracing.com/parts/SUM-G7950/