Hi, I have recently got my 6" batch style operational......When I built it I had on hand an old 50 gallon metal barrel from the 1920's, it is exceptionally heavy, 84 lbs to be exact. twice as heavy as today's barrels and twice as thick. The only thing I have noticed its a few minutes slower in radiating heat. my old wood stove which I replaced had 14 gauge metal as have today's barrels, they are lighter and faster to radiate to heat......as for draw I assume it has minimal effect as is absorbs heat, the air volume diminishes and is routed downward through your mass in the same fashion a thinner bell would do. A tall stack adds to the exhaust draw also.
how high is your stack above the riser floor ?