I gotta do a two tier stacked cake for 30 people. I have been going back and forth about what size will be good. Should I do two 10in rounds for the bottom and two 8in rounds for the top or two 8in rounds for the bottom and two 6in rounds for the top. Each round will be split and frosted so when their stacked it will be four layers of cake with icing in between. Help, what do you guys think??