To cutout the center of these doublers I drilled a 1/4" hole near the edge and then used a coping saw. It takes a while but it does work. I went through a couple of blades. In the end I found that an application of candle wax like I have been using on the band saw helps things along. I need to apply the wax several times. Once the parts were cut out I used a file for the straight edges and a sanding drum in the drill press for the curves. This cleaned things up nicely. I finished the edges with 220 grit sand paper and some scotch brite. For sanding the inside curves I wrap the sandpaper around a 1/2" socket extension. This seems to work well.