I used three of them, they worked like a charm. Funny you should mention that-- today I was at the grocery store and snatched up a wedge of Parmesan cheese and commented to the old lady that you were selling your wedges in stores now.
She said that she would love to see me try to use one. I don't see why it wouldn't work, Parmesan is a hard cheese.
I thought about picking them up for you, but thought you were probably making plenty of them since you had some to burn.