I would love to make the Cat in the Hat, hat for 30 people. I realize I will need some support in the middle, etc. Will I need a center dowel and cake plates between?

Yes, you will need a central dowel down the middle of the hat into the head of the cat. The hat itself will need cardboard plates with supports inbetween.....which will also make it easier for the hat to be cut. Whenever you think you might need supports for a cake you are creating....you do!