That's a great looking build for sure. I have a couple of questions for you. 1) Did you put any venting in the floor area to create draft? 2) Have you attempted to do controlled heat runs? Have you got steady 220 temps held for more then 3 hours? Or even lower temps.
I was looking over your build and could not see any additional drafts to bring in cool air. Your build is kind of like my food warmer / proofer build posted in Other Builds on the forums. To manage my temp I had to add more draft.