Project out of mothballs after awhile. My enclosure would not allow clearance for the Dura-Vent 60 degree angle needed. My chimney and pipe is routed to the rear of the oven. The first picture shows what was needed for a transition. I was able to use the cheap stovepipe from Lowes to make a dry run and ensure good exhaust when the oven was running. After cutting about 15 pieces of brick, the transition was complete. I'll need some of that 1/8 inch ceramic insulator between the face of the transition and the cement board which will lay pretty much over it. Hopefully the setup will exhaust well, I'll know this weekend, plan to get a fire going.