Ahh I didn't think about the ash. I can weld a capped piece of 1/2" tubing on the back side of the nut so the threads r protected. Thanx for pointing that out. Anyone ever do it this way?
That's how I did mine and I love it! My stack has a plate on it that seals flush and my air inlet seals tight, just like yours, which allows me to shut down my smoker totally! I dig it!