Be sure to check out California Scientific.
https://motorcycleinfo.calsci.com/R1200RTprod.htmlThis guy offers two styles in three sizes each for the RT.
Mine is the 'Standard Width' 'Large' (pictured on the red bike on his page. Black bike has the wide version)
I'm 6'2" and it works well for me so far.
use the yr button at the top of the page, and note that his measurements on the size chart are taken on the convex side of the shield.
The rest of his site is interesting, actually it's a large blog by an engineer that's been around and has a lot of advice to share.