I've been looking at this as I'm planning a multiple overhang column. You state a 15lb minimum and that this is the what the smallest ones weigh, but don't state an average size of the "platter". The 20" plus is a bit too large for my application but something in the 15" range would work. How do i try and get something in this range? ie if I were to order 30lbs would I get one larger piece or two small or a larger and smaller etc... I realize you can't be exact in order fulfillment but is there any sort of ballpark figure to go by?