can I run two 2.125" exhaust at 40.02" instead of one 2" exhaust at 80.04" Feldon's calculations cook chamber height 18" width 25" length 43" fire box 17" diameter length 25" size differential 99% chimney 2.125" inside diameter length 80.04" intake at 2" diameter need 5.42 five 2" holes and one 1" hole all on bottom of burn box. cylinder is enclosed in a box and adjustable vents on 2 sides that are both 8.5" x 2" - just one of these would equal 1 vent if it was a square fire box. box around cylinder is just .125" stainless steel to make mating it to the cook chamber easier. I ran two so wind is not a factor. one will probably be always closed. fire box to cook chamber opening 2" x 22.75" which equals 45.5 calculations call for 45..39 the entire smoker is stainless- so coming across 4" or larger stainless pipe for my chimney is not a normal scrap item where i work. This was made and altered off an old tilt skillet from our kitchen at work, it has a nice 1/2" thick steel plate that has a stainless steel skin on it for the bottom of my cook chamber. I just welded stainless on the lid, to lift and gain more cooking room. I have not fired it up yet, and want to get everything right before doing so, so i have a fighting chance of getting it right the first time.