There's a strong slk component welded to a mid 1930's Airflow, which is seen in Eric's first concept with the split window rear and windshield. I see the typical German rear end if a Porsche, that being a bit longer would resemble the Cayman. I believe the Cayman design was influenced by the Cross. I also see the Studebaker Hawk in there too to some degree. So basically, the design is a melding of classic design, and that's why our cars will never lose that timeless design and looks, no matter how old they get. Someday these cars will be regarded much the same as the MB Gullwing, as far as design goes.

edited: and yes I forgot to mention the Auburn Speedster too. But basic pony car design. Long nose, short rear deck, reminescent of the P51 Mustang, or in this particular case more like the ME-109, which was the inspiration for the Ford Mustang which got all this going.