Gotta go with Dave on this one. I Have always had better luck dividing my inlet requirement by 3, then placing 2/3 of my inlet requirements on the door below the fire grate with 2 independent vents. The last third is located on the fb door center line such that the bottom of the third vent is no more than 1” below or 3” higher than the bottom of the fire grate. All three vents are full open until the cc is up to temp. Then the top is closed, and bottom two are used to stabilize the cc temp. Once cc temps are stable, the top vent is used to regulate the cc temps for pretty much the rest of the cook. I only settled on the design after testing with multiple thermocouples rigged in the interior of the cc to measure heat distribution based on firebox door air inlet design. It took several weeks to complete, and by the time I was done, I had built and tested 6 different vent designs (and as many as 3 variations of some designs) in both calm and controlled wind conditions before settling on the 3 independent vent configuration as described. To be honest, it isn’t perfect, but the results proved to be the most consistent entry over the range of testing.
Ironically, had I only used the temp readings indicated on the door thermometers, 5 of the 6 designs would have “passed” on the first test.
However, the thermocouple measurements told an entirely different story about what was happening behind the closed doors.
Granted, many other variables play a big role in cc heat distribution (exhaust size/ location, plenum design/location, etc) and it is entirely possible your design works extremely well for the cookers you build, and if that is the case, stay with it. But, I would be interested in seeing what some instrumented testing shows.
