... I reckon the buffetting has more to do with the low pressure void behind the screen than it does from forward wind blast. Unless you use a screen the size of a barn door (or an RT) I don't believe you'll do much to alleviate it. Except possibly by fitting Tobinators.
... I follow the Jaygee school of thought. I'm 6'1" and have the seat in the 'high' position, but I have the standard screen raked right back and I don't find buffetting to be a serious issue until I'm hitting ban territory. It's a useful reminder to cool it (that and the fact that the wind noise obliterates my autocom music)
... Helmet shape also seems to be a factor as previously mentioned. I'd been using pure domed profile Arai lids without a problem, when some smarmy salesman persuaded me to invest in an AGV GP-Pro, which is both lighter than my preferred Arai and all aerodynamically sculpted "to reduce wind buffetting" according to said smarmy reptile ... Bollocks ... the AGV, despite the claims and light weight, is like wearing a barn door on the ol' noggin, whereas the Arais produce less Buffett than a live performance of Margeritaville (what a shame they seem to be eliminating many of them from the range in favour of a load of Carlos Fandango F1 stylised cobblers!)
... See if you can borrow some different lids from your riding buddies (or even your friendly dealer) with and without baffles, air dams, rear spoilers, go faster stripes, rippled surfaces and experiment a little to find what works for you.