Al,
I have incorporated that slip fit myself in the
design Bill Jepson and myself have been working on - but my welder is terribly
slow.
Our design has duel cool air tubes, the outer
acts as heat shield as well.
This is it awaiting the outer shield to be rolled
and welded.
The small tube you see is cool air which helps to
purge (and cool) the exhaust from the muffler.
The outer shield will be similar to what has been
suggested on here.
Can't tell you what's inside, only to say it
diverts the shock wave.
George ( down
under)