I suspect, truth be known, everyone starts with a hand out of a car window. That's the aerodynamics. The efficiency part comes in comparing the entire life cycle of a butterfly to gasoline exploding 20,000 times a minute.
I was drawing sports cars in high school but I can't lay a hand on an example at the moment. I was in college when Bruce Meyer created the Meyers Manx with buggy headlights and an upright windshield. I drew these:
I still like the idea of that lift-off top. Today, I'd make it the front half of a tapered bubble, so you could lift it off and store it on the back.