Agree with Carter...
Depending upon the variety I'm making I will either go with my 7-1/2" Tomme mold or my 8" hard cheese mold.
The Tomme mold does make a thicker wheel of cheese while I really like the look of the 8" since the mold is not tapered.
Either way, the wheels look very impressive, once finished.
If you don't have store bought molds, they can be made from PVC pipe.
If memory serves me correctly, Cater has some larger diameter molds on his website. Not sure about that. You might check the link in his signature line.
I can't go above an 8" mold right now because my cheesepot is maxed out at 5 gallons.
Regardless, 5 gallons makes a LOT of cheese!