I had uhge slices and I think I did 8 servings. Hard to remember. You can make the slices smaller and get 12 I'm sure. Teh origional recipe doesn't have a suggested servings either.

I used an 8 inch spring form pan. You can try experimenting with a 9 inch to make it larger and thinner to see if you can get more servings. I'm not sure how the bake time would be effected, so definetly experiment before party.