I'm doing a 4x2x18. Not because the BP needs the height, but just for the aesthetics of my set-up. It's going to be 3 pieces, all 4x2x18. The bottom piece will be a storage cabinet base, then on top of that, My Cal King, and on top of that, my BP. I got the extra height so that I had more storage space and because my cal king will climb and use every inch of her enclosure. I wanted all 3 pieces to be congruent so the BP gets the same size as the rest.