I finished this build a while ago and the smoker works amazing (thanks Dave, Rib Wizard & Squibb) unfortunately I want more cooking room. So, you math wizards out there, how do I figure this out? 1. I want to remove the door and build a box on top of it, (see attached internet photo). 2. I'm guessing I will have to change the size of the air inlets and possibly make the stack bigger or longer. If so, how do I calculate this? 3. Will I have to relocate the stack to the side of the new box or can I leave it where its at? Original Build Proposed changes Internet photo showing what I want to do. Internet photo showing what I want to do.