The smoker I am building is nearing completion. As a matter of fact, all that is left to do is to put in the slides for the racks. I will get that done today. Almost everyone on SMF knows that I do not cook with a thermometer, however this smoker is a little different. What is the trick about putting the probe in a potato? My smoker is air tight with with the exception of the chimney and I plan on tightening up the damper on it. Do I need vent holes in the bottom? How big? How many? Do they need to be adjustable? The size is about 19 X 21 X 40. It has 1 1/2 inches of insulation everywhere except the door and it has 2".