But can it process a roll of 16 mm with two ounces of developer?

Mine is a length of black ABS pipe, cap on bottom, filler spout (just a piece of gray PVC in a central hole in another cap) on top -- and then a length of smaller pipe with a pair of caps glued on, the caps turned down on a lathe so they're a drop-in fit for the larger pipe and length cut to give enough space to pour chemicals in and out (the bottom end of the PVC filler spout is notched to ensure that a floating core won't block chemical flow). Film wraps onto the outside of the core, emulsion out, close it up, and develop like any other inversion type tank (there's another cap on the PVC filling spout).
In order to ensure the dyes come out of the back surface (for films that need it), pull the core out after a little fixing and unwind the film to stand in a tray of (reusable) fixer. I've gotten great results with various microfilm stocks (Copex Rapid is best -- sure going to miss that when I run out). I don't seem to have a photo of the tank itself, and haven't found it yet (still unpacking my equipment, likely to be a while before it's all done) -- but here's a result.
View attachment 245985
Kiev 303, Copex Rapid, Caffenol LC+C, scan from print.