In the avantco unit, I was using a probe connected to the PC temperature controller, so the heating element was turning on when the water was too cold, and turning off when the water got to the selected temperature. But the heating element still retained heat in it, and the water would continue to heat about 8 degrees more. It was also quite slow to come to temperature for ripening.
I do not seem to loose much heat during ripening or resting the curd. I think the volume of milk, plus the lid, plus a towel thrown over if needed works just fine. Those simmer plates retain some heat as well. After turning off the burners, I still get 3 to 4 more degrees in the pot. I was concerned about too much direct bottom heat, but with gentle stirring it seems not to be a problem.
I wonder what the volume is on the steam table pan you mentioned. I suppose an 8 inch deep full size pan would also work..... Aiming bigger!