Sealing the exhaust:

I get tired of bolting again and again the ryobi muffler to change the gaskets, so finally cut out from 5mm aluminum a flange squared and drill in the shape of the motor exhaust, then bring it to a guy who is our aluminum guy that welds all our custom made mufflers and made my own eith a lot of noise reduction. To be sure about the sealing and have no bolt losening I drilled and tapped the holes to 1/4 and used allen scres. That is the best solution of all.
Tato