I built one of these a few years ago and used the center section of o 30 gl drum so I had a little more height s I could use 2 cooking grates. I also leave the bottom air vent closed and used replacement air dampers for a 18 1/2" wsm on the front of the kettle like on the wsm so air flow and ash are not a problem. I also built a charcoal basket like some use in the UDS using the original SJ fire grate and sized for The SJ. It burns for 16+ hrs holding steady at 250 or whatever I set it at. Good luck I hope this helps. I love mine!
UDS, Mini WSM, Horizontal 55 gl Grill/smoker, Keg-A-Q, Smokey Joe, Weber Baby Q 100, Snap-On Epiq, Weber performer.