Since bikes are kinda tall and narrow,the convention has been to streamline them as a 2-dimensional flow airfoil section rather than the 3-dimensional flow 'template'
With 2-D flow,the lowest drag is found when the bikes length is about 4X it's width
The big thing is safety! You want to go slow with development.A crosswind gust could potentially push you out of control.
Check out the Vetter Challenge bikes at the Motorcycle Forum for examples of designs which are working out well for their owners.
