How do you all figure out your cake servings on a carved out cake? I've never had to figure out servings on my creations that were sculpted because they have always been for my family. It's obviously easy on traditional cakes because wilton has provided us with those lovely charts. I was asked to do the University of Michigan M logo carved out of cake. I plan on printing out some template for myself to use to carve it out. I just don't know if I can realistically make one small enough for my friend. She only wants 15 servings but said I could bump it up to 20. The cakes I saw looked like they probably served around 40...just guessing! It has so many tight corners and looks like a pain to carve out, torte, and ice! Do you all normally charge for the cake the was carved away since it's essentially part of your cost. I don't make enough cakes to use the scraps for anything else like cake balls. It just would go to waste.  Here is a photo of what she wants the cake to look like. She wants it iced with the star tip in buttercream which my poor hands hate to do! I told her I don't do this type of icing anymore because I don't want arthritis but that doesn't seem to matter. Oh well but any advice you could give would be appreciated. If anyone has made a cake like this maybe you could share your experience on the difficulty of the cake. 

The amount of batter used.?

I'm not sure yet. If I go with an 10" square two layer that's 18 cups of batter. I am looking for a good template to print out now to see if a 10'' square will be big enough to carve out the M. A 10" serves 30 according to wilton charts but once I carve away I get confused on how to calculate. I absolutely suck at math!!!! It's embarrassing but true!