Im a bit dubious about that new CDG wing. Even if that central hollow does leave clean air at its wake, the car following behind has to position himself more or less at the centerline of the car he is following to achieve the benefits. If he moves from side to side ( in an attempt to overtake for example or unforced following a turn) he'll hit the turbulent air left over by the rear wing positioned on top of the lead car's rear tyres.
That sudden disruption of air could lead to disastrous results.

Again, I'll be convinced when it works for real and not just in somebody's CFD's simulations...