If you look in this directory on my website
Index of /graphics/MotoGuzzi
you'll find a number of photos of the Guzzi GP dust bin fairings that were developed in Guzzi's wind tunnel.
The fairing use on this Honda is an aftermarket item designed to appeal to the cafe racers of the period (late 50s early 60s) and could probably be improved a fair amount. NACA ducts instead of those air scoops would be a good start. The fairings on the Guzzi flat singles didn't need scoops like that:
cheers,
Michael