Someone posted a Rally car with a raised rear spoiler recently, but I can't find it now. It had fiberglass pieces that came off the C-pillar about 4 inches higher that flowed into a Bonneville type spoiler with a Gurney flap at the tip (IIRC).
Here's an example of a successful 4-bar linkage that attaches above the window. No reason why it couldn't be the C-pillar.
https://ecomodder.com/forum/showthre...tml#post397858
The struts, the decklid, the back window and the boat tail[?] constitute the four bars.