Fly cutter on drill press table. Note clamps, everything secured to large plywood sheet. I had machined up a ring (but didn't use it), but more I looked at the fuel valve, cover plate (left-both-right) and the indicator (red knob) the more I realized I didn't want to touch any of it during annuals. Easier to slip floor out with the larger hole in place.
Andair fuel valve has pre-dimple locations for countersunk rivets. Only two of three locations can use the floating nut plates. Third needs a standard nut plate, or a plain nut.
Cover in place, nice fit.
Image three is my quick set up for router trimming. 1/4" metal plate is used as a guide and to clamp large sheets in place. Pencil lines on the plywood show where to clamp the plate. Make a quick pass in the wood to show where the cut line is. Viola simple trim station. Hard to see in the photo but I had some 3/4" x 3/4" aluminum angle. I'm trimming on side a little short so it if flush against a 5/8" tube.
