I've been riding with a National Cycle "Street Shield EX" windshield on my VN750 since April. This past weekend I swapped it out for a Memphis Shades 17" "Memphis Slim" shield. I chose the 17" height based on the fact that the Street Shield EX is an 18" shield, which I'd found to be a very good height for me.
I'm giving up on the National Cycle one because I dislike the mounting system: the top 2 brackets attach to the handlebars and partly obscure my view of my tach/speedo gauges, and the bottom brackets attach to windshield via some glued-on plastic ball sockets that have both come off already in just a few months' time. Very annoying. The Memphis Shades quick release attachment system is much sturdier (all metal parts using nuts and bolts, no glue involved) and does not attach to the handlebars. It did require me to relocate my turn signals (from mounted next to the headlight to lower on the forks, next to my horns), but I happen to think that looks better as well.
What I've found is that the Memphis windshield is more vertical, lacking the rake angle the Street Fighter did, which means the height is actually a bit higher (relative to my eyes) despite being 1" shorter in height. Even with the shield mounted as low as possible, the top of the shield comes to just under my eye level: if I look ahead to the horizon I'm looking over the top, but if I'm looking at traffic in front of me (like an approaching intersection) I'm looking either through the shield or, which is worse, right through the line of the shield's edge, like a bifocal.
My first reaction was to swap it out to for the shorter 15" version of the same shield (they mount identically, so I don't have to do anything other than swap it in and return the larger shield). But then I found this diagram and text on the Memphis Shades website:
Most riders like to be able to see over their windshields. But in order to do this and still get ample protection, the windshield must reach up between the tip and the bridge of a riders nose. If it doesn't, a rider will experience mild to severe buffeting.
Obviously the diagram is based on a different seat height and/or mounting location on the bike, as I am a 6'2" rider yet the 17" windshield comes up to my face between where the 17" and 19" mark is in that first picture. (I have a Mustang saddle, which I suppose lowers my height an inch or two.)
Since at least 80% of my riding time is spent riding in local city traffic as I commute to work, I'll take the comfort of looking completely over the windshield with the 15" height over any potential "severe buffeting" for an extended highway ride. However, I have taken long highway rides and don't remember any "severe buffeting" with my earlier, "shorter" shield.
Just the same, I'd appreciate any stories from more experienced riders in terms of windshield height, riding comfort and visibility.