ok I think we messed up with the chimney, height. it does extend down into the cook chamber. our thought was to extend it lower into the cook chamber so it does not have to go as tall outside. thought over all length was what mattered not how far on the outside.
Chimney size is 3.5in and 35 in tall but we added the extra volume we needed with a 6by3 in tube inside of the cook chamber. the 2 air inlets on the fir box are 2by6.
our pit looks like the top photo that Columbia1 drew. here are some photos