webergrubbin, I believe you need about 24" from the coals otherwise you would be just grilling instead of smoking. With a diffuser plate, my guess is you could get below that 24" range. All of the drums I have made use (almost exclusively) the original lid that came with it. My recent ones use a lower grate & a upper grate that sits on it with "legs". Good luck with your build and post pron!
Cookshack sm055, UDS, Smokey Joe, Southwest Pit, couple of Weber kettles, an old gasser, and a weed burner.
Gary, KCBS -CBJ
Certified Nebraska MOINK Baller, KCBS - CBJ
Semper Fi, when in doubt empty the magazine