I'm building a smoker that will be run on propane. The inside dimensions are roughly 70"h x 31"w x 28"d. It is made of steel and will have 3" of insulation. My question is where do I put the smokestack? In the middle on the top, or out the side and have a 90 degree elbow going up? I am looking at using a 4" stack with damper and of course air intake will be in the bottom door. Thanks