I have a RV 13" spinner and base plate. How does one layout the screw holes? I have determined the spinner circumference and divided by the number of gaps between the screws and was about to transfer this distance into a two hole drilling fixture. I am thinking of drilling the first hole (cleco diameter--1/8") and then clecoing in this fixture to drill the second. Then moving it to the new hole and drilling the next. And so on until it meets the first hole. I expect that the last gap will not be exactly equivalent to all the rest but it should be close. Then I will place the spinner over the base plate and use the spinner as a guide to drill the base plate. I am not a machinist and only have a drill and hack saw to make this fixture with. I was thinking of a four inch length of 0.063 aluminum folded over the lip of the spinner. This seems to me a wonderful opportunity for some machinist savvy person to make this drilling fixture more robust and accurate and offer it for sale. (btw, I am not building a metal-riveted a/c so I don't have a lot of hole lay out experience) Or, tell us another way one can make this happen.