There's a picture a couple pages back in this thread with that very answer. I don't know if engine performance is decreased any. If you are going to spend money on a new exhaust that isn't a MACs tuned pipe for you Tower 75, you can consider the Davis muffler as well. Though a clunky strap on, I have run them on several different planes and they do quite well on top of not robbing power. The big reason for that is that it isn't just an expansion chamber, it has an inner pipe that the exhaust after expanding in the main area, has to flow through further reducing any unspent fuel noise.

For the MACS header and pipe though you'll need a 2890, 2891 or 2892 header and an 1160 or 1060 and 1260 pipe. Course the exhaust is still pointing the wrong way. You could even run one of them Double quite marine pipes that they sale over there, if'n you want to add 250 more dollars to your exhausting solution.

Or, buy one of them vibrating pumps and leave the stinkin muffler off. At least you'll know where it is, with your eyes closed!

Think I'll try the silicon thing first. If your silicone keeps coming off, drill and screw the exhaust pipe with a small machine screw. Then put the silicone on over that. If you have someone that can tig weld a ridge on it that'll give you something to hold onto it as well. Shouldn't cost much at the local machine shop.

EDIT Hey looky there, there's that picture I was talkin about.