I decided I wanted to work on something besides wiring today, so I got out the plans for the spinner backplate. I located the S-602B doubler, the S-602-1 backplate and the the S-603 front plate. I deburred all edges—some were pretty ruff. I positioned the doubler ring on the backplate by inserting 4 bolts thru the mounting holes. Then I match drilled the doubler to the backplate with a 1/8” drill inserting clecos after each hole. After all holes were drilled, I went back and ran a #30 reamer thru each hole, replacing the clecos as I went. I traced the inner edge of the doubler onto the backplate, then removed the doubler. I made a ruff cut out of the inside of the backplate with my dremel cutoff wheel, but it is going to require quite a bit of filing and sanding to get it to match the doubler.