Took about 3 hours from my busy napping schedule to get back on the Lincoln. I made a slight adjustment to the front fender line and placed the rear window opening and a rectangular panel that sits just ahead of the rear trunk lid.
It took several hours' worth of studying all the source pics I grabbed last week to work out just what the Mark III's real shape is. On first glance, it's just a slab-sided brick with a knife-edge fender peak that runs the length of the car. It's not obvious just yet in the drawing, but there's a very subtle "Coke bottle" effect. The front-most point on the front fenders is the widest. The body narrows very slightly just at the rear edge of the doors, then swells just wide enough for the rear wheels before narrowing again at the rear bumper.
So it's a subtle slab-sided brick.
Good thing about CAD is that I can erase lines without messing up the screen.