My husband is a machinist and has decided he wants to make me a custom tray for my c5050. I would like to use it with the Ultra Light strobe arm set up (I haven't purchased this yet), but he wants to machine a ball attachment and the tray out of a solid piece of stock. What we need to know is what is the size (diameter) of the ball found on the Ultra Light set is so it will all work together. Thanks!