Joe, I would recommend using the stock exhaust manifold. At least during
your early flight testing. That is all I've ever used and it is bulletproof.
I just passed 560 hours TT. Experiment with mufflers later. I'm happy to
just continue using the stock manifold because it is worry-free. Broken
exhaust systems aren't good on pushers!

Richard Sohn: what is the status of your 1-rotor? There is a guy at my home
field building a Fisher plane, don't know the model name. It requires two 60
HP engines, he was inquiring about the rotary. I told him it wouldn't work
unless he used one-rotor engines with aluminum side housings.

Perry