I am looking for opinions here. I am making a rainbow cake (so 6 layers) for 40 people. She does not care what size or how many tiers. She's leaving it all up to me. What would you guys do? I was initially thinking of using 12" layers to make it a single tier, and then providing her with the cutting guide for 40 servings. Or would you recommend a 2-tier? Thanks in advance!