Rudy, It doesn't matter how tall the hoop is. You would use the same weight for one that is 6" tall or 12" tall. The PSI stays the same based on the diameter of the follower. The weight does change if you go to a different diameter hoop. The square inches is the follower, not the volume of the cheese. I know that's a bit of a head scratcher but HEY it's just physics. (sorry JD)
Here's a little chart that shows weights needed to achieve a given PSI for various diameters of mold. Just find the diameter of your hoop at the top. Immediately under that is the Follower Area in square inches. Now go down the column to the PSI that you want to use. The weight needed will be to the left. For example if you are using a 4" hoop it will take 25 pounds to press at 2 psi. Now look at an 8" hoop. It will take 100 pounds to achieve the same psi. !!!!!
Hope that helps.