Hello, I need help on a 3-tier cake with the top tier is a 3D football cake (2 cakes filled)? The football cake will be filled & covered in buttercream. 

What is the best way to build this 6” cake and how should I stack it as a top tier?  Do I need to place a cardboard in-between the football cake and how should I dowel/secure the football top tier cake on the 2nd tier?  

** I’ve attached a photo showing the design that’s close to what I’m making.