Not to get off track of the trike idea, but here is a page about turning a Honda Helix into a streamliner.
Last Vetter Fairing
When I have asked around on forums about streamliners, there have been comments about sidewinds and getting pushed around in high winds. With a slow moped vehicle this is a deal killer because it could push me into a passing vehicle. I prefer riding a two wheeler but the problem of getting pushed by sidewinds makes me believe that the three wheeler is the superior design for this use.