I can't remember what size hole I drilled in my CP, but I do remember taking all of my spade bits and comparing the diameters with the diameter of the shaft of the spinner. I ensured that the hole I drilled was bigger than the shaft so that if my screw holes weren't lined up right it wouldn't interfere. Since the spinner itself covers a great deal of space, you can afford to make the hole a bit bigger than the spinner shaft itself.