Bomber I think that the vents in rear quarters window will work in two ways…
1 . when the car is stainary i.e in traffic or pitlane heat can rise through these vents.
2 when the car is moving the vacuum affect of the scoop tray underneath flowing in a sealed box trhough the rad and out boot will draw in fresh air from the window vents.
found this mk2 toooo
need to speak with these guys to get tips too