I need to do a tilty cake to serve 20.

I was thinking of doing 5-6-7 for the top tier and 7-8-9 for the bottom. Will that work?

I am terrible at figuring servings for those!

On another note, I need to stop saying yes. I am not complaining at all just a bit overwhelmed by all that I have committed to for this week. I had one order, then two and somehow this has morphed into 6 consultations and 6 orders!
Can I say YAY and YIKES at the same time!

that is more than enough. Have you thought of using just 2 layers for the top - the 5 & 6 would still be more than enough.
Good for you getting orders