Here's my simple set up. I'm very pleased with how it works, I may have just gotten lucky with the sizing/ spacing. It deflects the main force of the wind off my chest at highway speeds yet allows enough for ventilation and has not gotten in my way off road/ on single track either.
It's thicker than it needs to be (just might be bullet proof
)...but I just used a scrap piece of lexan that was available to me.
Bolted directly to the number plate, spacing is accomplished by simply slipping a piece of hose/ gasline over the bolt between the two pieces, also providing a vibration free rubber mount.
Side views to show spacing.