Good write-up, thanks for doing this.
Total time for this project is two hours tops, including wasting 30 minutes wrestling with one clamp on a connecting pipe / muffler union. After breaking the code on that, total time would be about 90 minutes.
Technically, you do not need a deep-well 13mm if you've got a long enough extension. The suggestion to support the muffler with a jack was a good one.
When you're actually pulling the pipes off the cats the looser the clamps there the better. Otherwise it will bind up at an angle. And make darn sure both the forward hangers are off their mouting bolts, or you'll be climbing back under the assembly, resting it on your chest and wrestling off the one that is still hung up. Or so I've heard....
Objects in mirror are slower than they appear.