Originally Posted by BigBobBQ
I am having the same questions, from what I have come to understand the evenly spaced 1/2" holes in the lid might be the best way to go. it allows the heat and smoke to exit the top in a more uniform manner with even distribution, where I have heard that the single 2 inch bung hole exhaust forces air to exit in one location causing some sort of direct line draft from the intake to the exit and is prone to causing a hot spot under the exhaust and in some cases a large difference in the temperature from the center of the grate to the edge of the grate. I am going to use the evenly spaced holes in the top for my first build as per the instructions on NorCo's build. Maybe some of the more season uds pros can chime in and elaborate on their experience. I may be totally wrong in my thinking but for some reason it makes sense to me.
I used the 2" bung hole and have not had any of the problems you are worried about.