Installed oil door on cowling. Cut out recess in cowling small at first and trimmed it several times to make sure it was the right size. Used the same technique with the door. Trimmed it to almost the proper size and then fit the hinge to it and drilled it to the cowling so that it ended up in the same place each time. From there I trimmed the door a little at a time until it fit perfect in the recess. Riveted the hinge in place and installed the Skyloc fasteners. Looks good!