[aerohead]

I dredged up a couple of cars which share similar curved-roof length percentages.
The Ford / Merkur-Scorpio 2-door, and VW 2000.
Both have around 38% aft-body, Cd 0.33, and Cd 0.25, respectively.
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*The Ford starts with a 25-degree fastback ( as measured from the horizontal ).
* The 'notchback' shelf / step is added, relaxing the rear slope to 19.5-degrees.
* A lower rear spoiler is added, increasing height and length, relaxing the slope angle further, to 16.4-degrees.
* Finally, the upper wing is added, creating a 14-degree slope angle off the backlight within an inch of the 'fast' template, and Cd 0.33.
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* Volkswagen just goes for the throat, with a simple non-porous fastback, of 14-degrees downslope angle, with a perfect match to Wolfgang Klemperer's Cd 0.15 Basic Body contour of 1922, coming in at Cd 0.25, 70.4 - inches ( 1,788mm) short of Klemperer's long-tail total length.
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* Klemperer's tail reaches a maximum rear slope angle of 24.5-degrees, exceeding Mair's recommended 22-degrees at 89% tail length.
This appears to be the same contour Toyota has chosen for all their Prius variants, since the Gen-II. Which, on the Prius, also happens to match Mair's transition region to 22-degrees rear slope.