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I have a RF offset with split top/bottom doors and here's what I can tell you:
1. I have consistent temps throughout my cook chamber (3 separate therms all within 5 degrees of each other)
2. Based on the construction, the lower corner opposite of the firebox (trailing edge of the RF plate) stays consistently COOLER for smoking more delicate foods like fish
3. I can open my lower door (which opens first when opening) and pull out the lower rack and have it open for a period of time and it does NOT affect the upper cooking chamber temp to the degree that I have to stoke the fire to recover the heat loss
4. Any heat I do lose with both doors opened it recovered quickly when shut
5. Once I have her locked in on my cooking temp, I chew through maybe 2 wheel barrels of split wood in a 12 hour smoke session
6. My smoker is trailer mounted and leveled to the trailer itself so raising or lowering the tongue immediately affects how well it heats or how slow or fast it burns wood
7. You can see my RF offset by clicking on the link in my signature