Hi all, I have got my hands on a 140 gallon air receiver tank that I plan to turn into a reverse flow off set. I've used Dave's calculator that was converted to excel so would someone be kind enough to check the results for me. They look pretty good but a second opinion will allow me to cut up the cylinder with some confidence that I'm doing the right thing. I also plan to insulate the firebox with some 1200 degree kiln insulation I have and use a glass door off a combustion heater so I can see what's going on with the fire. Thanks in advance. Adam.