Let's see if I can explain this to you in Long Distance Touring aspects.
. We generally want protection from Bugs, Direct Rain, Heat, Road Stuff ( that vehicles kick up in front like small rocks, dust, etc. ). Optimal is the line of the top of the windshield coming just below your line of sight to the road. These are not barn door type shields but well designed tall touring shields. I never like the look through type shields on some major touring rigs. I had my BMW R11GS, R11R and R1150GSs set up like this and did many 600 to 1000 mile days chasing rallies about the country. I even got my DL1000 like this with the stock windshield by using spacers and had no problems on a round trip to California with a couple 700 mile plus days in the saddle due to a miss calculation on my part getting to Hollister to have a seat redone.
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There is a large difference in doing day rides with your upper body in good clean air flow and doing the miles in all kinds of weather day after day for a few weeks or months on the road.
IN my YOUNGER DAYS, I toured all over the Lower US with no windshield. As I got older my body wanted more protection without going to a touring rig. I just did get off Adventure types bikes with longer suspension due to age, legs ain't what they used to be to hold up with just the tippy toes or sliding my hiney over. Still miss the Adventure bike ride though.
I also need a bike that I can stand on the pegs when doing loose gravel or just to relieve the hind end.
I can get what I want with the shield by adding another to the existing shield but would prefer to have it one piece even if it looks a bit strange being so tall.
Gosh, should just look at some of the touring shields for The BMW GSs out there. But, they work. Function over beauty and form.
I happen to like the engine, transmission and seat height of the 1250S Bandit and will keep striving to make it a great sports touring bike to fit my needs and wants.
I wear ear plugs on all my bike rides out of town and at times, even in my noisy truck on some of the roads that pass for asphalt roads down here.