Great FAQ, one item of note however. You say in your faq that inconel exhaust is the best & you're probably right however one thing to note with INCONEL.
We usually use INCONEL 625 on submarines and if (God forbid) you get a crack in INCONEL, you could be chasing/repairing that crack forever as it will continue to spread when trying to reweld (unless you're very lucky). Like I said, given that,you're probably right about the INCONEL exhaust. I just thought I'd throw that little tidbit of info out there as a "potential" concern.