Hello All, Glad to be here! I am new member seeking an advise on a design.It is vertical smoker (stainless steel Members Choice) w hich sits on the 16X8X8 concrete block and I am adding off-set fire box (Concrete blocks 16X8X4). My primary fuel charcoal and mostly wood. Upright base is 48" tall concrete base and stainless steel MC cabinet sits on top of it. I need an advise on the size of opening from firebox to upright piece. My firebox is 31X19X20 and side opening to Upright is 8X8 Is 8X8 is big enough. I would like to be able to adjust temp from 120F-250F. Thanks for advise Tom.