For the oval hole in the other attach plate I decided to drill a single hole and then cut the entire oval using a coping saw. This seemed to work quite well. I did some sanding with the drum sander. When I overlayed the parts I discovered that the two ovals were not the same size. After some measuring I discovered that I had measure one of the holes wrong. I was too small. Whew! Making a hole bigger is easier than making it smaller. After marking the correct hole size is used a round file to open up the hole.