Being either directly involved with various projects, or as an interested observer in others,.... I've kinda developed my own biased views of fairing use. I've watched the most basic, a face shield, evolve in many ways over time,.... while eye protection was the primary purpose, comfort was the major factor of consideration. From simple "goggles" and "shades" to fancy helmet shields and various "windscreen" fairings, comfort was jus not to be sacrificed in such, at any speed! And that includes the comforts of stability and control. Taken to the extreme, you have an automobile, hahaha!
And who hasn't tucked tight, elbows in, knees together, head down,.... minimizing frontal resistance on a downhill accent? Still won't beat out the "Guerra Superman"!!! LoL!!! Frontal resistance at "low speed" is pretty big,... give me a tailwind any day! Overcoming it for a gain in speed or efficiency though, is usually met with inconvenience and discomfort, and comfort isn't something we care to sacrifice so casually, outside of competitive activity. Recumbents and velos weigh that balance quite carefully.
At greater speeds, DRAG becomes a bigger factor and often overlooked, unless your "rocketing" or "sailing" at speed with minimal or no ground contact. Then a "tail" or "rudder" becomes important as does some "lift" perhaps from wings of a sort. Heck, Wilbur and Orville barely made bicycle speeds. I find those hybrid "ice-sleds" like that above to be simply AMAZING!!!! My experience in "hard-water" sailing is actually quite minimal, although rather exhilarating.
Nope,.... I'll be comfortable with some good eye-protection, gloves maybe. Although that "body sock" Aero-Edge looks like a nice addition to my rain wear! Comfort, ya know.