Is this going to be an offset RF? Considering you are going to use "gas", it may as well be vertical so you can save a lot of fuel. Make sure that you open the bottom below the "gas burner" up so it gets plenty of air. Take a look at the gas safety thread on the home page. Most people on this site will try to discourage you from using gas it is just too dangerous. But hey, welcome to the crew.
Making memories.
Current Smokers: Backyard RF Offset and Hybrid RF Offset trailer rig with Cowboy cooker and fish fryer, always room for more........
For reverse flow what other option is there. From all the plans I've seen they show like that. I didn't figure what the heat source mattered. On the gas thing I made a duck blind few years back and it has 2 cooking ovens / hand warmers in it and it is heated by propane and not had any problems with oxygen mixture. Those are both 24"x24"x18"deep. And the exhaust goes 22 feet to exit opposite side to exit
Looks like a nice job you're doing there. If you went with center feed, you can still go RF it is just going to enter the CC on both ends. Gizmo, and FishlessMickey have done several center feed. With this process you want to have a shadow plate above the flame then a space then the baffle plate. This reduces the hot spot in the center of the plate. At least with this process you won't waist most of the fuel, it will all go to heating the CC.
jm2cw
Current Smokers: Backyard RF Offset and Hybrid RF Offset trailer rig with Cowboy cooker and fish fryer, always room for more........