the clamps arent eally pulling the boards together, more like hold the boards at a right angle. i plan on about 5 or 6 on short sides, 11-12 on the length, because i want it to be VERY solid. i will probably uy a length of PVC as well and figure a way to hold it securely to the side and pour resin between the box, and the pvc to round out the vertical corners.