Cd is only part of the story, there's also A(rea). Those numbers are:
- 1.35
- 1.40
- 1.62
- 1.44
- 2.38.
I didn't remember the slide-on camper as being part of the sequence, so thank's for that.
The large pop-up increases the frontal area 'unnecessarily' (it's a stowage bin). Drawing a curve from the slope of the windshield to the top front edge of the pop-up would be most like the high roof.
With this body the stagnation point is at the front edge of the hood. Everything below that is going under the body. I'd make it straight and push it out to the hood-line.
The other problem is the square corner; look at the later models. The air dam, by my estimation, is only 1/7th the height of the front fender. That's why I'd suggest adding a 1/4-round outside the headlight.
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Lot's of room on the pop-up for solar panels.