I like the idea of doing something retro and period correct, which your font certainly seems to conjure.
Curving the rear corners so it ends up being more of an arch at the little end does seem to be the trend, and would flatter the rest of your curves.
I think rear vision is surrendered unless you are going plexi-glass roof with a Prius type rear mini window.
Have you thought of making this an aero camper? I have not seen this done yet. I don't mean "pop-up" style, I have seen that. I'm thinking more like the green template humping the roof and then tapering back.