I agree it takes a bigger hole. The way I read Timeserts info an M5 insert takes a tap dia. of .238 and a drill dia. of .199. They call for a #8 drill.
An M6 takes a 1/4 inch drill and tap dia. is .290.
You would think Husky would have come up with a good fix for this problem, as common as it is. I did read they have a muffler with 3 bolts. Also the 346 muffler with the brace is said to fit. I find that hard to believe, as the 350 is plastic.