Some loads require lateral securing as well to the crossrails.

yeah, I don't either. they look to be "tracks" rather than "rails". I assume some sort of clip/bracket would be required to attache a strap.

probably more aerodynamic, but a lot less utility.

fj..

This looks like the same roof rails that are on the a3 in europe (or by special
order in the united states). I don't think there are any companies in
the US that have rails for this system yet, although in the UK thule makes bars
that fit. There's a photo of an a3 with thule bars that fit somewhere in the a3
forums...