OK guys...I'm ready to do it. I have acquired a 275gal oil tank & a small (4'x4' I think) utility trailer (both free!!) for my build. I want to make it a SFB, reverse flow. So my thoughts are, stand the tank as it would normally be, on it's feet, and bolt/weld it to the trailer. Then attach the SFB at the back end. I have the calculator, but I may need help understanding what size I actually need exactly. As for the reverse flow portion of it, I'm a little clueless. Do I need to have a certain amount of space under the cooker and how big does the opening into the chamber have to be? Thanks guys & I'll post pics real soon!