The fish tail muffler has been in service for years on motorcycles and other
machines.

Its poor service life behind a rotary is due to the shock wave dropping to
subsonic by applying its energy to the flat sides of the design. It is both
a rflective and an impinging design.

If saw cuts are made into the long axis of the fish tail shape and bits of
metal are welded in place to prevent the flexing (and fatigue death) of the
pieces, this design might be found quite effective.

Years ago I tried one of the big Suitcase Flowmaster mufflers on the racer.
A reflective design and very effective. In one session of 45 minutes, all of
the baffles were hammered loose and piled up at the exit pipe and the sides
of the muffler swelled up like a giant pillow. The reflective design was
changed to an impinging design. I was far from home at Sebring Florida so I
cut open the Flowmaster and flatened the sides. I welded the baffles back in
place with more than a spot weld here and there. I drilled through both
sides behind each baffle and installed solid 1/4" rods to keep the flat
sides from spreading open again.

I moved it to the very rear of the body where the heat load would be
reduced.

That muffler lasted the rest of the season. It was sinfully heavy and really
too big for anything but a big GM car, but it worked great on the rotary.

The Spintech or similar I think will fill the bill. More likely a
combination of two styles, or one style behind another. Any system that does
not include equal length headers leave a bunch of HP on the table.

Lynn E. Hanover