Hey guys I have a 200lb (50) gallon propane tank I'm making a smoker out of. My firebox will be 20"x24" 1/4" thick. I plan on making the firebox with a lid on top also so it can be used for a charcoal grill when not smoking. I used the formulas and came up with 11550 si cc which gives me 46.2 for Fb/cc opening. Playing with the numbers I came up with 3" ed and 14.283 ad. The question I have is this, is the green area your finding for the half football the only thing you cut out or will you take that and flip it to the top like a mirror image so the cut out will be round? I'm kind of confused on this part. Also wanted input on firebox size. I know it's a little on the big side for what I have but I wanted the extra room for ash pan and wood basket plus enough space to grill on. I don't plan on stuffing it full of wood so I don't think it'll be a problem. What do you guys think?