My SIL has asked me to make a 3D Dalek cake for my brother's birthday. I'm just wondering about the construction of it. I'm planning to do something like this

I was planning to use my giant cupcake mould and my 6x4 inch tin to construct it. It's probably going to end up being about fsix layers of cake and probably pushing around 10 inches tall.

Do I need to put any supports inside it? like a cakeboard and dowels? Should I put in a centre dowel to stop it slipping around when I'm trying to carve/cover it?

I'd really appreciate your thoughts!