Here is my primary muffler for the renesis as made by planexhaust.  Welding was perfect and the fit only needed a file down the bolt holes.  At $600 that is cheap compared to anything here in OZ.  The bellows was an E Bay special at $20 made from inconel. Sadly I missed the rest of them, still one is better than none.  Neil.

Looks like it will work Neal.

The RX8 engine is a bit easier to muffle. If it is no quiet enough
add a long, hollow, 4 inch round under the fuse. That will not add much drag.

Paul Lamar