The other thing about a fairing is that on a TourEasy the fairing extends to about where the rider's hands are. On most SWB bents, the fairing is not that close to the rider. The result is a 'draft' behind the fairing, and the wind flowing over the top hits the rider in the chest. That negates any aero benefit the fairing might have had. The other thing is what shortboat mentioned, the smaller your frontal area is, the less you need a fairing. Still, a V-Rex benefits from one if it's shaped properly.

On a related note, underseat panniers won't be protected by a fairing; they'll hang down in the lower air flow. If you want speed, you should put your gear in an aero shaped tailbox or seat bag. So while they're very useful, they're sort of at odds with the use of a fairing.