Good Afternoon, Bob,
With my Chromega 8 x 10 drum, I normally use 10 to 12 ounces of solution when I process four 4 x 5 sheets of film. I've used 8 ounces (Technidol) with no problems at all. I suspect even 6 ounces would be adequate, but with cost not being a serious factor for most B & W chemicals, I prefer to err on the side of caution. I can use up to 15 or 16 ounces in the Chromega before some of it comes out during the rotation.