Help! How do you figure the servings for a topsy Turvy cake? I would quess to go by the smallest layer size in each tier, but the best directions I found shows using 3 layers of cake (6/7/8, 8/9/10, or 10/11/12) for each tier. Using the 3rd layer is throwing me off. Anyone have any ideas?

i just made one too and was trying to figure it out. i am erroring on the side of less servings but taking the servings of the middle size in each teir should be about right.

i also figured that when cutting it i may cut the shorter side of each teir slightly larger than the taller side of the teir since it will have an extra layer of cake in it.

i am looking forward to reading what others have to say

Well, for "real" servings I would go by the smallest layer in tier.
But to calculate the price I would try to get it as easy as I can:
count the middle layer as your tier and give additional fee as extra for the topsy turvy.
Mind you, here you never get price per serving - the people want 10" cake, you either have a price for the cake with filling and pay for the decorations extra or the baker calculates it this way and give you a price. The customer either likes the price or not. Nobody cares for price per serving - and mostly people have no idea how many serving there are.