This is not a normal vertical, see the thing about vertical is the majority of the heat goes straight up into the cabinet for cooking. But with an Offset FB you really have an offset not an vertical so yes all the rules apply to that style. The calc is your friend.
Current Smokers: Backyard RF Offset and Hybrid RF Offset trailer rig with Cowboy cooker and fish fryer, always room for more........
I compared vertical smokers for size and BTU rating (propane). It looks to be a 2:1 ratio of BTU/cook chamber volume is the ideal. I know my own gasser is not quite in that range and is under powered.
With wood (post oak) coming in at ~7000 BTU/pound and charcoal at ~9000 BTU/pound you'd have to make your fire basket sized accordingly.
If it's tourist season, how come I can't shoot 'em?
One thing to consider is that a complete combustion can be attained in an offset because of the wasted heat. So I like the offset type better than just vertical.
Making memories.
Current Smokers: Backyard RF Offset and Hybrid RF Offset trailer rig with Cowboy cooker and fish fryer, always room for more........