I have been a member for a while now and have done lots of research on RF smokers. I got a 120 gal tank out of storage that I got from work and it measures 24x64. My neighbor got me 3/16in steel plate from where he works. I have 6pcs 2'x2' that I will make my fire box out of. It gives me 143% size differential. I have a 2ft x 4ft to cut down for the RF plate and 2ftx4ft expanded medal for cooking rack. I put all the info in Feldons pit calculator and it gave me a 16.78in opening fire box to cooker. I am not sure how deep to set the fire box in though. Also how much of a opening I need where the RF plate ends and the other end of tank. I was trying to go off this build a bit because of the similar sized tanks.I was using a lot of the sizes and info from this build. http://www.smokingmeatforums.com/t/121415/my-100-gallon-reverse-flow-build/60 I have been smoking on a Webber 22.5 kettle and really need something bigger. I think I will buy an trailer to mount this to. I will post pics as I build it but I think it will be a slow build. All advise is welcome.