According to Ferrari they create downforce without ugly wings.
Unlike conventional buttresses where the rear window is short, flat and vertical in the 599 GTB the rear window is long, inclined and curved.
Also unlike conventional buttresses they are open so they redirect air from the sides to the area behind the rear window, usually a negative pressure zone.
I think that by filling in the negative pressure zone they also reduced drag, Don't you think?
BTW such flying buttresses were used on the Honda/Acura new NSX prototype
