Cinder Block Verticle Smoker ~ Direct vs Indirect

Couldn't you put in an extra set of rack runners above the firebox for a removable heat diverter? Then you would be able to try it both ways.

Is the top of your firebox open or closed in? If closed, I would think you could maintain good heat althought it might take a while to get that mass up to temp.

I am right there with you.
Due to the winters here in WI, I chose to go vertical. From my research, it will heat more quickly and being fire brick will have more stable temps in the cold.
My WFO is incredible at holding heat from even a small fire. I plan on using the same insulating concrete behind the split fire brick liner.
I plan to make a domed stainless steel inner liner for the ceiling with the top flue extending down into the cooking chamber (dimension not figured yet) to maintain heat and smoke.
I will be updating my build thread very soon as the rain and chit weather seems to finally be behind us now...

Not sure if this helps but some ideas from my research.

Couple of thoughts if you still want to go indirect/offset (looks like ThermalMass's build is not an offset). If I understand your original description, your firebox will be concrete (cinder) block with a fire brick liner. You could just stop the firebrick liner one course (about 2-1/4 inches short of the top of the outside layer of block, cut a (i.e. 1/2 inch) steel plate to fit tightly and cover with refractory mortar. You might consider extending the steel plate into the cook chamber a few inches to act as kind of a deflector plate. Based on ThermalMass's experience with his WFO, I'm pretty confident this kind of setup would get you plenty of heat & smoke. Final thought, you will probably want to control your fire at the intake side, so some kind of firebox door with adjustable air intakes should be part of your plan. Good luck, this sounds like an exciting project.

Just BS said:

I haven't figured out how to enclose it yet, but that is the plan. I am leaning towards pouring refractory concrete into a mold. Still working out the details. :wacko:

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Ooooohhhhh granite - functional and pretty:clap2:. Please make sure you take a lot of pics of this build. I can already tell it is gonna be a good one.

Just BS said:

Dwfisk, That is an excellent idea. If I set a steel plate down with a piece of CF Board on top of it and then enclose with refractory morter and finish it off with a nice piece of granite, that would make for a nice work surface too! Brilliant.

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I also have a vertical smoker. I know a few guys who have cinder block smokers that have a hard time maintaining a temp but that is in Illinois in the winter. Seeing as you are in SoCal, I don't think you will have that problem.