Mike, that is such a cool thought. I do not know but am wondering if even that wee bit of restriction close to the engine might cause some slowing of the engine.
Just an off the top of my head thing but would some exhaust heat tubing. (can't find a link! forgot what it is actually called) as a spacer work?
Dunno but really like your thought. Found this on the forum; http://www.google.com/cse?cx=partner...ust&gsc.page=1
Really looking forward to seeing what you come up with.