Some quick updates:
I'm contemplating moving overseas for a few years for a job opportunity. If so, most likely the removable mods will go into storage and I'll sell the car.
Magnetic attachment of anything to the outside of a car is no good, according to Utah inspections. The Kammback has been shelved since June.
The AHB latch was left open due to user error and the lid flipped open on the road, damaging some sheet metal. I've repaired it, but haven't added a secondary safety feature yet. See the next post.
I faced a headwind during a trip recently. My best estimates are 28-30 MPG, level ground, ~72 MPH ground speed, 25-35 MPH headwind, ~45 MPH gusts. So that would roughly be my MPG at around 100-105 MPH, if I had a suitable gear. Here are my best guesses on the car's performance parameters right now:
Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com
Cd: 0.30
Crr: 0.12
(Maybe higher Crr right now: we're in winter tire season, they might be a bit higher than the all-seasons. The Crr end of my coast-downs has registered at around 0.12 with the (crappy) Les Schwab all-seasons. So I should be able to reach 45-50 MPG at PSL (neutral wind condition) just by getting some decent LRR all-season tires... on paper.)
So the project overall is somewhat successful: I can get mid 30's MPG trip average in very unfavorable conditions without sacrificing speed, with loads of storage volume. And the tail has proven it's ability to hinge on contact, avoiding damage.
I think the underbody is where I've primarily failed aerodynamically on this project, so far. It looks awful and so far I've left it untreated.