The gasket works more than fine on my 3 gas engines including the DL50. The trick is to mount the new muffler or header and never touch it again. If you have so many issues w/ mufflers coming loose, you might want to check your prop balance.
First image after 2 hours break-in at 2500 rpm. Second image 100+ flights. Gasket isn't leaking, nuts still in place, even w/o washers because of a lack of space. I used the white heat resistant thread locker from Advance Auto Parts.