Do not overtighten the screw/nut. I've been told by O.S. that the main reason that these screws break and the rear half falls off is because the screw is too tight.
When the muffler gets hot and expands it expands more than the steel screw can handle. This causes the screw to snap.
Poor design IMO but what you have to deal with. Myself, I purchased a length of all-thread at Home Depot and cut it to length. I then installed metal stop-nuts on both ends and have had no failures since. Others at my field do this successfully too. Not as pretty but functional.