LoneAl...Checking the muffler bolts before each takeoff is not enough. They can be tight before takeoff and lossen in the air before landing. Usually the engine quits and you may lose the plane. Here is what I do. Take the muffler completely apart and use RTV automotive silicone high temp sealent on all of the joints, including the flange to the engine. Use blue Loctite on all of the threads of the muffler, and on the threads of the muffler mounting bolts. Check the muffler frequently. If you see a leak anywere or anything getting lose, redo everything. Eventually you should redo it. I know people that have lost 3,4,5 mufflers in the air. I have never lost a muffler.