I bought an Adventure sized Z-Technic (Z2423) for my GS and the buffeting was so bad I was going to sell it, send it back or whatever because I couldn't ride behind it. After trying it for several miles on several different days and wondering why I was stupid enough to spend so much on a windshield that sucked, I found the answer by accident.
I reached across my chest to unzip a sleeve and the buffeting just stopped. Unbelievable!
The touring W/S in combination with PIAA 520's was causing wind buffeting to come UP off the lights and under my helmet. After moving my hands around to see where the air was mostly coming from I took off the PIAA's and the RCU mount and that WAS the problem.
Wanting to keep my lights, I decided to try some add on deflectors and they worked really well. After a year and a half behind the Z-Technic I'm still completely happy.....it's a quiet ride even without ear plugs. I can ride with my helmet shield open at 50 MPH with very little noise. The windshield itself is a pretty expensive solution but it absolutely changed my GS in terms of being quiet at road speeds. It's warmer in the summer but quiet all year long
and really good in the winter.
The photos aren't great but they show the simple fix I used. I cut some some black 1/8" plastic to pieces about the size of a playing card and used insulated cable clamps and a couple of small screws to attach to the 5/8 tubing Z-Technic uses for the W/S support frame. After the test ride I never even took them back off even to remove a sticker that was on the plastic I cut. The Velcro on the left is just to route the cable for the GPS.
I'm 5'11 riding on a Russell saddle in the low adjustment slot with barbacks on the handlebar. The PIAA's are 520's on an RCU mount bar.
Hope this helps someone else who might have spent money on the Z-Technic and been disappointed.
I like mine all year long now. It's almost as quiet as the marketing video they use to try and sell 'em!