[aerohead]

Hucho tells us that the premise of streamlining is to move the separation point rearward,minimizing the turbulent wake, or eliminate the separation altogether.
If you wanted to ere on the side of safety,you'd stick close to the Template as it in indicated for use.
A caveat would be Buchheim's 23-degree roofline.He's a PhD and had access to a world-class tunnel at VW,and his research indicated that rear slope tangent angles could be pushed to 23-degrees,rather than W.A.Mair's 22-degree limit (which is what the 'Template' is based upon),given the proper preliminary curvature.
I believe you can see Buchheim's profile with the latest iteration of VW's 1-liter car.
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General Motors has had very stringent requirements for outward vision (which I understand having driven the 1st-gen Insight and recent Prius) and I believe this has certainly been part of their design criteria.