For anyone finding this thread now or later, another option I looked at was Tom’s design.
There’s a video on the post above that one and a bit further down some more information about that design where Tom says:
I don’t think the size of the pipes is real important as long as the inner one is an inch OD smaller than the ID of the outer half pipe. I think the half pipe could even be made out of well braced PVC.
I didn’t have the right combination of pipes but will keep this design in mind in case I find the right pipes.
Not to get off topic but in between the post linked above and Tom’s comment about the half pipe possibly being made using PVC Matt has a video of a nice way to make charcoal.
I’ve been collecting my charcoal from the house furnace.
The heat from burning out the tars was used to heat the house and the glowing coals gets grabbed with tongs or sometimes a little shovel and put in a cast iron Dutch oven. Next time I check the fire that charcoal has cooled and gets dumped into a bigger metal barrel with a good lid.