[elhigh]

There's an old, slightly dirty joke:

Q: Why are turds pointy on the end?
A: So your butt doesn't slam shut.

The atmosphere doesn't like slamming shut. Any taper you can add to the tail is good. Since you're planning adding tail length, plan ahead to taper it. If you can extend that tapering further forward then you can make even more of a difference - the goal is to reduce as much of the absolute tail's cross section as possible, while still adhering to the ideal aero template (find it in the Aerodynamics sticky). Don't forget you can taper in the sides as well as the roof. You give up storage capacity but pick up a smoother, quieter ride and lots of miles per tank.

As to the nose, increasing the radii of the corners is good. It doesn't have to be structural and you may be able to make that take the form of new rear view mirrors, or simple add-ons at the front corners below the level of the windshield.

With the rear engine you can do all kinds of smooth underbody, which you already have on your do list. That will yield big dividends.

Big, big project. When you start your build thread, I'll be subbing that.