It's just freebeard. I'm not that Important. Also, authoritarians buying into their own B.S. It's priceless.
A rolled strip for the edges. Simple curved sheets with curved edges as necessary. A '58 Impala style divot for the 3rd brake light. I'd increase the radius progressively, with a half-ellipse at ChazInMT's green line. Or go to a Gothic arch, with a peak in the center. The area inside the green need be no larger. Or you could have a flat triangle (level or slanted) from the rear window to the top rear.
Square tubing for the bed rails, windows and weatherstripped openings.
Props to those that get something done. I've got pieces rolled for a boat tail for my Beetle. But I'm not confident I have a means of attachment that won't wear through the paint. Sometimes it takes months for the light-bulb to go on. A pickup bed looks a lot easier.