Well, I figure the best way to see what happens is to try it on a real boston butt. I popped in the grocery store on my way home a picked up a nice looking 7.5lb butt. It was only $1.69/lb, so the risk/return seems acceptable. A smarter man would put a grate on the coal tray so if it falls, it'll get a bit toasty, but won't be covered in charcoal. I think I'll do that; I can't abide the thought of good pork hitting the coals.
Well, at any rate, the experiment is in progress. It went on at 2:30pm. I expect it'll be done around 7:30pm.
Any bets on whether it'll survive in one piece?
...
You could add a support to the bottom part of the sling to help hold it together. I'm thinking if you removed the handle from something like this, and used the "basket", it would give a lot of support.