Aero-bike - why have I not seen this?

[Grant-53]

One thing I notice is that a tail box can act as a seat back providing resistance. A great deal of study has gone into seat and leg position. Aero bars properly adjusted can be rather comfortable too.
Stability in cross wind is improved by fin area and down force. Rounded sides reduce drag that we feel as steering input. I mount my fairing on the frame so the wind loads do not affect steering.