The chimeney height and diameter arecritical parts of the design.
Warm / hot air rises.. the higher the chimney the faster it draws.
by experimenting with height/ diameter one can control the the temps.. IE if have issues keeping temps down increase height and or diameter.
If you adjust the bottom air draw (restrict) instead you run into things like bitter flavours, air currents that influence chip burn times...
Both influence hot spots, and smoke distribution inconsistent temps at different locations in the smoker.
Also will need a trap bend in the chimney near the bottom.
The warm air also has moisture, this condenses on the walls of the chimney and runs back down into the smoker.
Note : this was the 'testing' stage, the vent now runs up the inside of the wall and vented out up under the shed eaves
All stuff I found out when setting up my smoker inside the shed. Initially had issues not get temps down.. and accidentally found the 'fix' when moved permanently into the shed adding the chimney... then came the condensation issue. fixed with a bend in the flexible air ducting at the bottom with a small hole poked in, and a 1L container to drip into.
Door seals.. clean the door and a good coat of vaseline on the opposing doors jamb area. Good bread of silicone on the door, close the door and leave for 24 hrs...vaseline stops sticking to the door.. perfect seal.
I did find that as time and heat went on the door tended to warp slightly and leak smoke.. to fix this , re sealed and placed several rare earth magnets around the outside of the door/ jamb as door catches...rather than 1 single catch.
Racks, chose something that can lay muscles and other small items on without them falling thru at the slightest movement of a rack.