Ok many of you saw my 1944 Army field oven I am going to convert. By my meaurements she now Called Gunny Smoker, will be about the size of a Backwoods Competitor model smoker but with less grates installed. I am trying to figure the Square Inches of area needed for the exhaust. The top of Gunny is hinged in two places and at the center hinge a gap equal to 3/4 inch by 20 inches long runs across the lid. That is I think a surface area of about 15 sq inches. Since this lid fits so well around the edges I thought about not replacing it but using that gap with a simple deflector hood used to deflect the smoke from the front. Will this work and is the 15 sq. inch area to much or not enoeph as an exhaust.??