i've heard so much about the ug 15's and 22's. usually the subject comes around to the roasting drums used on these models. anybody got the juice on this subject? cast iron comes up 99% of the time as owners romantisize. they sound fabulous. what exactly are/were these drums made of? where does cast iron come into the picture? i'm looking at a roaster that has a double ply steel drum w/ space between the plies. is this what the probat ug series had/have? where is the cast iron? this forum is very helpful. thanks! also, any specs on btu max and minimum on the old ugs? right on!