@Ringo
There seems to be a bit of flow seperation though, just before th slot gap, then it gets fed again and it seems some air is attracted to that.
This cutout creates low pressure, this detaiched air will prbably just take the easiest way out with the gurney tab there. I dont think there is a significant loss of df, the low pressure area and the air between the end plates and under the wing help over come that a bit. Now saying this, the end plate trailing edge(vertical part) got a gurney, by this the air just probably goes straight through there, the lowest stripe of wing wouldnt follow the flow line anyway.
Wont say this is all wrong here, but surely interresting. the dark blue fade just in front of the slot gap suggest flow seperation.