Getting this thread somewhat back on track seeing as people would rather argue.
This paper
Design and development of the Sunswift eVe solar vehicle: a record-breaking electric car from my collection of aerodynamics papers is quite good and may be of use to you
Cars are 3d and so only the centreline shape (in still air) will have true front to back flow, a template may work for a certain shape of certain width with certain curvature in certain places, but that is not necessarily representative and small deviations can, but not always, cause large effects.
The above paper shows the refinements to a design rather than turning a template into a car, same end result, different starting point.