Ok, now we're cookin'- Nothing like starting a new design. :)
So if we are looking at a total height of 48 (or 60) inches so:
Mixing box around 12"x12x12" (7.5 gallons)
10" main column, 24" (30") = 7.8 gallons (9.7g)
Total volume: 15-17 gallons
I'm leery of the 6" neck, and 10" cup. I'd...