My new oven won't fit a 16 inch pan, so I used a 16 inch half circle pan for the first time. Is there anything in particular I need to know about assembling the 4 pieces for the tier? For example, do I line up the seams parallel or perpendicular? I am nervous since this will be the bottom tier of a rather heavy cake! Thanks!

Perpendicular is all you need to know. Nothing else special. Oh, and buttercream vertically at the seam in each layer.