Poor man's Aptera
I was looking at the pictures of the Aptera and it stuck me, its basically a small airplane fuselage. So how about an old cessna cockpit and fuselage minus the wings and tail, with a 400 or 500 cc liquid cooled twin cylinder motorbike drivetrain at the back. Even a single cylinder would work but it would probably rattle your brains out after a while, I wouldn't go any smaller due to the lack of torque and high rpms can't be all that good for fuel efficiency even though they are fun...
Front suspension and steering should come from something light and narrow, a suzuki swift for example. Grafting the front end parts would be a bit of a challenge but it would be light, aerodynamic, and well sealed up to the weather. I guess some cessnas even seat 4 with luggage but I imagine the rear bike suspension wouldn't handle huge loads for too long.
Ian
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