@Knifemaker - Glad you found the thread useful
I'm finding that my little gas fired, reverse flow COS (cheap offset smoker) is actually doing a better job on the meat than my Big Ugly Drum, and I believe that is because there is no direct radiant heating of the meat at all. Just the hot smoke that wafts around the end of the horizontal plate, and small amount of gentle indirect radiant heat that the plate gives off. Mine is just two layrs of sheet metal; I'm sure that a more substantial plate would work even better.
Of course the UDS does have the advantage of being able to smoke a much larger quantity than my little gas unit.
I plan on upgrading the Ugly Drum with an added layer of putting a large metal pan or bowl over the charcoal basket, to eliminate the direct radiant heat path, and also allow me to add moisture vapor to the hot smoke, as well as act as a heat sink to steady temps. That may also be something good to incorporate into a horizontal design, since you are starting from scratch.
I have seen some very nice reverse flow horizontal offsets made from heavy gauge, large diameter gas cylinders, like an old propane tank.. Those have the advantage of much higher mass for increased even-ness of temperature. Be sure to keep us updated on your build.
