Your mold will likely only hold curd from 1 gallon. You can generally expect to get about 1 lb. cheese from 1 gal. milk. You could easily make a 4 gallon batch in the 8” you describe. The cheeses that cook at higher temps, like the cheddars, have less curd mass than lower temp cheeses, since the curd expels more moisture during the cook. I made a 4 gal. batch of Colby and it filled my 6” D X 8 1/2” mold to the top. If you’re going to build a larger mold, I’d suggest you go to 6”. The reason is that with larger diameters you need more weight to get a similar press. Pressing is figured on the basis of pounds per square inch of surface area. For instance, with my Gouda I needed to press at 4 PSI, which comes out to about 110 lbs. Unless you have a lever type press, it’s hard to get that much pressure.
Hope this helps.
