Having repeatedly looked at the bbc video following the tail-wing movements it is clear that the RB6's wing moves down (rotates around a horizontal pivot point) with increased aero-load. The obvious fact that by the tail-wing flexing/rotating downward is to change the AoA hence reduce top-speed drag and downforce. What would be intersting to know where the pivot -point would be located.
The options are obvious:
1. The entire tail-wing which would be a comprimised setup, especially in high-speed corners because drag is reduced, but so is also the downforce generated.
2. The tail-wing is rigidly fixed to the underside of the car (including diffuser), but the flexing point is part of the undertray (forward of the diffuser) causing the diffuser get lower to the ground when the aero-load increases on the tail-wing. Since the tail-wing is an exposed aero-element and changing the AoA reduces the drag-coefficient, but has the side-negative effect of then also reducing downforce. This could be perfectly compensated by allowing the diffuser to move with it as well. Lower diffuser means increased downforce with no negative side effects. And when the car is normal or low-speed or static (parc ferme) is has normal ride-height. So Horner is right that it is not a ride-height control system, it is a diffuser-height control system
Obviously, the above is just academic and open to all your points of view or comments
GReetz,
S.
Though the regs say no part of the construction should have a degree of freedom relative to the rest of the sprung mass, i think the FIA should align their static tests with this ruling. It leaves loop holes if the static test for example is a 10 pound weight for only a 1cm of defection, when in fact that part of the car experiences 50 pounds of force on the track, unbeknown to the inspectors. And the team can't be blamed for it because they followed the rules. 
