There were some legitimate, albeit fixable, issues with the Corvair’s design and handling. Porsche had run into identical handling and “tuck-and-roll” problems with a similar design and abandoned it during testing.
Just about all Porsches prior to the 924, 928 and 944 were of the RR-configured air-cooled engine design, whether the 356, 911 or even 914. I was under the impression that Chevrolet were imitating that design with the Corvair, down to the turbocharged flat six in some models.