Sorry bout the slow reply. Slots are allowed in the central 150mm of the car, whether it be in the beam wing or the main elements of the rear wing. The idea is that the top section of the flexi wing flexes the 20mm required for the load test under 100N of force, guaranteed by the lowered endplates, but under the greater force on the track, pushes the tunnels down closer to the track, harnessing ground effect, to some extent.
TM.