If you use the National Cycle Switchblade windshield they make a pair of chrome lowers that go underneath the windshield and run down the outside of the forks. Theymount on the same hardware andare supposed to provide even more wind protection. I have also found that the amount of buffeting depends on the head/cross winds.
Enjoy,
Jeff

 

I got a Shoei RF1000 helmet with a built in spoiler- no issues- my old helmet buffetted over 40mph regardless of windshield or not