I need help please. I need to make a cake that feeds 20-30. It is to be shaped like a wedge of watermelon. Not a small triangle, but a long triangle shaped wedge (you know, that you would cut the individual triangles from if you were actually eating a watermelon). I've been looking at lots of cakes on this site. I'm not sure how big to make the cake, knowing that a large amount will be carved off.

If you make your watermelon like a slice that is shaped like a 1/2 circle instead of a triangle, then you can carve out of a 1/2 sheet (12x1 and not lose a ton of cake but still accommodate your serving size needs. If you google watermelon cookies here on CC, you can see the shape I am talking about. Good luck!