Greetings! I'm mostly a lurker here, as I've been considering a Forza.
I own a 2002 Silverwing. Shortly after I bought it about four years ago, I found out that the stock windshield was simply awful, with lots of helmet buffeting. I installed a Givi AirFlow on the bike several months later and have now had it on the bike for several years.
I am a total fan of the AirFlow, at least on my SWing. Buffeting has been completely eliminated. The windshield can be lowered for more ventilation during the warm parts of the year and raised for more protection during the winter and early spring. The weather here (Sacramento, CA area) gets quite warm in the summer...often 100oF or more for long periods of time...and pretty cool in the winter (32oF or lower). The AirFlow does very well in all these conditions.
Obviously, I can't say how well it might do on the Forza, but my guess is that it will work well.
Just wanted to throw in my tuppence ha'penny here...