I just finished installing a Parabellum tall windshield on the K1300GT. Great product! I can now ride at an indicated 70 with my visor open, and Laura now longer gets the helmet buffeting like before.
(I believe the stock item is great for most people, but I'm 6'-6", and Laura is 5'-8" and long through the body.)
The disturbing thing was that the windshield screws are assembled dry with no retainers. If I learned nothing else from the '63 Bonneville, it was that threaded fasteners must be held by something more than force of habit! (Ours now have medium-strength thread lock.)
My concern is that if someone does not secure these screws, and some loosen over time, the wind thrust would be distributed unevenly - possibly causing the windshield to crack.