no door needed
I have 6 1/2" close nipples around the bottom of my drum, usually cook with 3-4 open, depends on how much meat is on the grill. I have 8 holes in the lid, 6 are 1/2", 2 are 7/8". I drilled out two of them to get my temps a little higher
I took a charcoal grate from a a 22" kettle and welded expanded metal around it for the fire box. The grate has 3" of metal below it for air and ash, and 10" above the grate. It holds 12 pounds of charcoal, and 34 fist sized chnks of wood.
The best run I've done is 12 hours with 12 pounds of charcoal, holding 225 degrees at the meat height. You're going to love cooking on this thing, when it's time to clean out, just tip it over.
I ran to loads of charcoal with a little wood to season mine.