All you need to care about is weight, stability, and
visibility. If you want to plod around at 30mph, I'd put a lot of effort into making the car visible. Aerodynamics mean little anywhere a 50cc can be legitimately used.
A good, wild example is the rolling egg...
Squibb's Moonbeam
The cheapest, easiest way to go is a scooter fairing. The engineering is done for you.
Just a thought.
- LostCause