The 4" chimney stack work great, I think I am going to add a 2-1/2" black iron pipe right above the 4" one going from firebox to meat chamber just becuase I am definitely loosing a lot of heat trapped in that top 3-1/2" of space. Plus on my cook yesterday I had all valves and intake holes wide open the entire time. I got good temps, but with everything open I really had no control. I'd rather have the ability to go much hotter than I need but be able to control it with the intake valves.
Anyway, thanks for all your help guys, I posted a new thread with my finished build (well, is it really ever finished?).