I have a supertigre 61 with the 2 piece muffler. It has the round header pipe that sticks out about 1 1/2" that the muffler clamps on to. It is the old style, not the silent. The question is, is there any tuning involved with this muffler by sliding it in or out? It looks like if it was installed all the way on it would cause some restriction in the muffler. Would I cut the excess stub off?

Do ont believe you will see any tuning effect, but you will see restriction with the muff slid all the way toward the engine, especially if you are running small props at high rpm. you can trim the stack if you want to run the muff close to the engine, it will reduce exhaust restriction.

All that's is required is to cut the stub at a slight angle and the restriction if there actually is one is gone. I have run with mine all the way on for years and no restriction was noted. I use them on other brands of engines as well.