Rick,
It isn't all "logical"...
I had the first version of the Cee Bailey, no "flip" in those, in a +4. When the better fitting version Two "flip" came out I went with a +2. Why, first the "flip" effectively "adds" the same coverage as more windshield height so I needed less + sizing to work... Secondly, HEAT
To simulate a +4 I suggest you put your OEM shield up two clicks and ride in the heat, that is about the equivalent of a +4
without the "flip factored in, and see if you still get enough airflow when you want it... Keep in mind you
can raise a +2 another notch, all the way to position five if you think you need it, but you
can't lower it below position one when you want more air...
Now for the "illogical".
From a purely aesthetic point of view I thought the +4 looked too big, the +2 "flip" gives more of a sport bike look in my opinion... That and putting too big of a "barn door" windshield on your NT might let one of those slow
Red NTs catch you...if you were going uphill against a F-5 force tornado headwind...