Hi , Thanx for the replies. I guess that I wasn't clear enough, I meant smoking only, and as per "thirdeye"s comment, the magic number is about 24". my concern is how critical it is since I found out that the distance in my drum is 16".
A lot of people have built drum smokers using smaller drums which would have less distance from charcoal-to-grate. And Pit Barrel
makes a Jr model that is about 30" tall, so that would be less than the 24" too. Also, there are hanging racks for the Weber WSM
smokers, so they too would have a shorter distance when used like a drum. There is also an option to make or buy a heat diffuser or vortex
style charcoal basket, but I think this may reduce the flavor you get from the fats dripping into the coals.
It just boils down to playing around with your set-up, figuring out any hot spots and learning how to control the intake and exhaust vents. When hanging meats you may need to cut a pork loin or rack of ribs in half. For me, the simplicity of cooking in a drum and the unique flavor make them a great cooker.