I'm thinking there are factors other than just adding more fat to the original ingredients , more stirring would equal less moisture in finished product , would it not ?
Would that not affect the finished product , less moisture = more solids = more protein & fat ?
Acidification times would also affect the amount of fat retained in the curd as well , I think.
Sweet whey contains more milk fat than acid whey, with 1 cup of sweet whey offering nearly 1 g of fat compared with less than 0.25 g in acid whey.
I'm guessing adding more fat , as in whole cream would bring the total fat up , but there may be other factors at play as well that will change the result.