Right now I'm working on a 3D Scooby cake and need some advice!

I'm doing him sitting up, below the collar will be sculpted cake 12" high, and the head will be RKT 6" high. I have all my cakes baked and I will need 9 or 10 layers to get the height I need, and I plan on hammering a wooden dowel into the base before I start carving the cakes, but my question is: can I just stack the 9-10 cakes without any support other than the main wooden dowel? Or would it be better to do 4-5 layer, plastic dowels, cake board, and then the other layers.