Just to be clear, there is no mention whatsoever in the SAE paper about a template, standardised shape, etc. There isn't in
any SAE paper that I have ever seen on the aerodynamic development of a road car.
And, as is so common with what Aerohead writes here, he correctly quotes, then misquotes, makes up stuff, and applies his own interpretations to what was actually written. Some examples:
- in the SAE paper (and my book) the spoiler is described as having one position, not two.
- the way the spoiler works, as described in the SAE paper, is substantially different to Aerohead's theory
- the change in drag is not related to a change in wake pressure in the SAE paper (or my book)
So most of the post is just Aerohead fitting a car to his theory. To a hammer, everything looks like a nail.
Note: The description of the Audi notchback / hatchback / fastback models was included in my book in the context of the required different
rear diffusers for each body shape, so my description of the fastback spoiler was brief. Aerohead hasn't read the SAE paper.