So, I've done two "test burns" the last two nights.
First night I just followed the instructions. Full chimney of Kingsford briquets.
Started at 5:30pm
110 at 6:00
200 at 6:30
175 at 7:00
175 at 7:30
Shut it down at this point. As most said on the web, the charcoal simply gets smothered by the ash in the bowl.
Last night I switched the legs from inside to outside and set the bowl on some 2x2 square tubing. This means the entire smoker can be lifted off to access the coals instead of having to remove the lid, rack(s) with meat on them, and the water bowl. I also used one of the racks on top of the bowl to hold the coals up.
Started at 5:00
325 at 5:30 (water pan's boiling)
320 at 6:00
290 at 6:30
240 at 7:00
200 at 7:30
At this point the charcoal was pretty well all gone. I chalk up the high temps and short burn time to too much air... so last night I made up a 4" rotary vent with 4-5/8" holes for the lid. Next is to try to seal the lid better, then I'll do another test. The lid sits on 3 brackets that also hold the grill. There's probably a 1/4" gap between the lid and body. Two options would be to add a gasket to the lid to try and close that gap, or instal a flange that the lid sits on. I'm going to try the flange, as it won't cost me anything. One hitch is that the body has a rolled lip, so a flange the same diam as the inside of the body won't go passed the lip. It'll have to be made in two pieces. Wish me luck!
Here' are some pics for reference
Air goes between the bowl flange and body, up and out under the lid. I'm thinking I'll choke off the lid first and see if that gets me the results I'm looking for... if not then I'll move on to the bottom.