Ernst Fuhrmann was head of the 928 project was he not? Wasn't the 928 his concept for an eventual replacement for the 911? Or was the 928 created in a design vacuum since Porsche was flush with so much R&D money in 1971? Perhaps that he lost his job to American Peter Shutz had nothing to do w/ the direction that Porsche was headed w/ the 928?  At the time (early 1970s) it was impossible for Porsche to predict what direction the US Government would take in terms of safety and emission requirements. The US market represented nearly 50% of Porsche sales at that time. The soft top convertible essentially disappeared from the US market after 1973, and there were real concerns that a rear engine car would not be allowed for sale  in the US. In hindsight people may tell you otherwise, but at the time the 928 was conceived there was real concern and serious discussion that the 911 would be removed from it's most important sales market by Government regulation. What people remember and tell historians, and what they actually believed at the time are often two different things.
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Carpe Diem--life is but a crack of light bounded by eternities of darkness (Nabokov)