Good point, Ben! One thing that's overlooked, I think, is the "Venturi" effect. That is, the flow through a smaller hole is greater than a larger hole, if the amount of air passing through both is the same. If you see smoke flowing from the top vent hole, the air coming in the small hole in the bottom has to be somewhat equal, which would make it flow faster. So, we really don't know what is going on inside the box, from an airflow perspective. I would think that the heat of the smoke box is drawing the air in through the bottom at a much higher rate than the air blowing out the top hole, so the lower part of the smoker probably has higher air currents than at the top, where it's diffused.