[aerohead]

I'm moving some of the bullet points made at the Barnard & Template thread to create a dedicated site where anyone can 'kick the tires' conceptually.
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Originally:
' Following the shape of any 'mythical' best shape ( ie. The Template ) when making modifications to existing cars cannot produce the best possible results ( Or if it did, it would just be complete coincidence ).
Julian Edgar
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'Best' is a subjective term, it's unquantifiable, and I don't know anyone in the scientific community which uses such language, so I'm going to reframe this thought experiment. And I'm limiting my comments strictly to aerodynamic technology. And I'm also limiting low-drag candidates to only those that a motorist could 'see out of,' and could service at least four passengers.
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'Following the shape of any of the three 'templates' which happen to coincide with the embryonic roofline contour of an existing production road vehicle, when making drag-reducing modifications, will enable fully-attached flow for the entirety of any chosen percentage of the 'template' length.
Since the 'templates' are a derivation of the lowest known drag contours recognized in the extant automotive aerodynamic literature, it's unlikely that one might find alternative contours which could exceed the streamlining capabilities of the three 'templates.''
Philip Knox ( aka 'aerohead' )
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1) Sighard Hoerner's 1965 book, Aerodynamic Drag' provides the lowest drag
architectures and precise fineness ratio at which the drag minimum is experienced ( 2.5:1 & Cd 0.038 ), from which the 'templates' are derived. If a body is shorter, the drag will increase as a function of pressure drag. If the body is longer, the drag will increase as a function of surface friction drag.
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2) Wolf Heinrich-Hucho's 2nd-Edition provides the solution to the lowest-drag automobile body, described as a streamline body of revolution half-body, which completes a streamline body of revolution via it's mirror image reflection from the roadway. The 'template' half-bodies produce Cd 0.076 in ground proximity. Addition of wheels increases drag up to the vicinity of Cd 0.126.
3) Then, Goro Tamai, in his book, 'The Leading Edge' suggests that the drag from the wheels can be reduced by approximately 70% by use of full, swept, wheel fairings.
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Current reporting continues to cite the 'teardrop' ( lay term for the streamline body of revolution ) as the lowest drag form known and applicable to low drag road vehicle design.
And presently, the two lowest drag offerings, The Lightyear Zero ( Cd 0.175 ), and the Mercedes-Benz EQXX ( Cd 0.1716 ), are found to inhabit the space occupied underneath the aerodynamic streamlining template, version-C, which satisfies (1), (2), and (3).
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It's my opinion that it's no coincidence that M-B and Lightyear are using this 'contour / silhouette ' as it appears to remain a benchmark for low drag, and has remained so for 113-years since G. Fuhrmann published his researches on it.
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I remain the student, and am fully willing to embrace some 'breakthrough' in road vehicle shape, however my library implies that about every shape which could potentially see light as a road vehicle has already been investigated, and for 'really-low-drag' our 'shape' options are extremely constrained.