Next I am cutting back the epoxy to extend 1/2inch from the edge of the oil door.
Measured and drawn cutting lines. Then put some circles in the corners to determine the center point of drilling for the curved corners.

I center drilled the circles and and then used the biggest step drill I had to drill up to the lines.
From here on, it's just a matter of cutting back between the circles close to the cut line using a dremel cutting disc.

Then I put the door back in place and started sanding and trimming back it's sides in order to get a 0.05" paint gap.

This is what 0.05" looks like

I used some wood spacers cut from a disposable wood spoon to test fit the gap on all sides. These wood parts are very close to 0.05" and were a great aid here and later on when evaluating the paint gap on the cowl itself.