Chris,

You will definitely need some shielding on virtually all the exhaust that is internal to the cowl.  I have used light aluminum on standoffs held with hose clamps, have used aluminum foil RTVd to the inside of the cowl, and have placed aluminum shields mounted between engine mounts, wiring bundles, etc.  The radiant heat will melt most any non-metallic object within a foot or two of the pipe if it is not shielded.

I have over 600 hours now, and the shields are doing a fine job.  You will know if you missed shielding a plastic conduit, for instance, because it will look like heat shrink. (Don't ask.)

That looks like a neat installation, keeping it under the cowl.  I ran over 200 hours with a similar set-up on my 13B before my (homemade) muffler finally melted.  After that I decided to put the muffler under the belly to get the heat outside the cowl.  Yours should last much longer with the Renesis.

Bill Eslick