I've had that tongue muffler for years. It was made to fit a C/L Fox 35. Most of the ones now available are for the 40 to 50 size C/L engines. It could be made very easy, by anyone with a drill press, and a few other machine shop tools. It's basically a chunk of aluminum that is about 3/8x1.25x1.25 (not exact measurements). Then it's hollowed out (from the side that contacts the engine) and holes are drilled into it for the exhaust to escape. Add a pressure tap and a worm clap, and you're done. A guy in Atlanta named Tom Dixon used to sell them, but the selection now seems limited.

As for noise, I ran one last on a Super Tiger 51, and then changed to an Ultrathrust muffler. The UT muffler was louder, primarily because of the hight pitch I think. The tongue muffler had a much lower pitch sound, and wasn't what I'd call excessively loud, but it was louder than a stock muffler.

I can try my Mini with both, someday, and I'll compare rpm and flight charachteristics. That concerns me, as C/L engines (of that time) were not screamers at all. They generally ran at fairly low rpm. These mufflers may not like high rpm situations. I'm in hopes that since the muffler was designed for a slightly larger engine (.35), that the muffler will have volume enough to allow a bit more rpm on the 25LA.

Basically, which ever muffler gives me the rpm, gets the job. With a stock muffler, I'm ahead of the 1 inch back from the spar point. With the tongue muffler, I'm right at it. Either way is sure to fly well.

Another concern I have is the GOO FACTOR. This muffler is gonna spew!