I'm getting close to completion, but I have a question. For the exhaust I used a dryer vent with 4" duct. The flapper portion (hood) will mount right to the top of the fridge, leaving about a 4 to 5 inch length of duct sticking into the cooking box. My question is if I need to have a stack on the exhaust with some kind of substantial length. I don't know if the extra length would provide some kind of drafting effect (venturi), or if the short pipe will work just fine. If you look back at the previous '38 post you can see what I'm talking about with the dryer vent.