The trick here is you need to locate them on the spinner 180 deg apart. I didn’t have a tapemeasure handy so and made a mark the spinner as a starting point and I wrapped a piece of masking tape around the bottom of the spinner starting at the mark and when the free end of the tape came back around the circumference I made a mark on the tape. I then removed the tape so I could flatten it out and measure from the end to the mark in order to get the spinner’s circumference. Then all I had to do was divide that number in half and make a new tape that same distance in length. I then put the new tape on the spinner starting at the mark I had made earlier and where it ended was half way around the spinner or IOW 180 deg apart. I now had the locations in which to make my cutouts. Here I used a template that I downloaded from Hartzell instead of following the plans. I trimmed the cutouts undersized and sanded it out until I had a decent fit on the prop. However, I couldn’t figure out how to twist the blades with the prop sitting on the bench to check for interference so I decided to wait until I had the prop on the plane where it would be easy to twist the blades. Now with the spinner cutouts trimmed, I located and drilled the holes for the attachment screws and went back and drilled and associated nutplates.
