After I painted the cowling's inner surfaces white and the paint dried, I riveted the oil door hinge plate to the cowling and installed the oil door. This involved installing a spring to the hinge pin: This spring kicks the door open if the camlocs come unlatched. With the door swung open, I should always see it whenever the oil door is unsecured. Swing check was great.
Image 2 shows the camlocs' initial fit: I remedied the button fit with subtle bending on the camloc button arms. I have to say, I'm not entirely satisfied with their flimsy construction. We'll see how they hold up to real use and abuse.
Oil Hinge riveted to cowling, Pin check
Door installed, closed position, buttons need aligning