I have a request for a 3D rainbow cake to feed either 20 or 25, the customer hasn't decided yet. My plan is to bake and fill a round cake with buttercream, cut it in half and crumbcoat, then cover in fondant and decorate. My questions are:
1. What size would feed 20/25? I sort of assumed I'd do a 40 serving cake & cut in half, but that would be a 10 or 12 by my standards and that seems pretty big to stand up even once cut in half.
2. Should I just make a 10" (about 20-30 servings by my standards) and stack the whole thing on it's cut sides? My cakes are usually about 4 inches tall. Is 8 inches too wide?
3. Do I need some sort of support, or will the buttercream be enough to hold the layers together? This will be traveling about 20 minutes by car.
Thanks in advance!