Here are some photos of my ongoing project two seater tadpole trike, considered a motorcycle in Virginia. The engine is a 9 HP Honda Diesel 432 CC single cylinder rated for 3000 RPM sustained. The tranny is a Harley 5 speed with the rest of the (rear) drive wheel components using harley parts. The harley starter will start the otherwise manual start diesel engine.
The front end is a 1971 VW beam axle.
As you can see the shape is exactly according to the ideal aero shape posted many times on this forum.