Ok so I've not been able to get as much done as I wanted to. It's been pretty cold here and my garage is unheated. So my motivation isn't what it should be. Combine that with all the holiday stuff and the kids and you get some slacking going on.
That said, I got the upper air vent cut in and functional, just not completely finished yet, and I built a proof of concept on the firebox door latch. Then I threw a couple of picnics on it and did another smoke. The Firebox door latch worked well enough to keep the warping to a minimum. A couple of times when I opened it up to feed it, the door sort of popped, but was easy enough to get back closed tight. So I'm going to go ahead and finish up the latch as I was planning.
The upper air vent made a huge difference. I can hardly believe it. At one point I had the main vent about 80% closed, the upper vent about 2/3rds closed, and the CC was pretty steady at 275. Just got to remember to close it when I open the FB door, I had flames shooting out of it at one point. It still burns an unbelievable amount of fuel, but thats just life I suppose.