Thanks for the link. I've seen Georgia Tech's work as PDFs. The competition for pneumatically blown slots is plasma actuators. I like blown slots because VWs have 1500 cubic ft/minute of cooling air exiting a duct at the bottom rear.
The picture to go with aerohead's drawing:
...done by a neighbor of his. From here; where there are
links to box cavity threads.
A full boat tail based on Thee Template is a heavy burden, but following Mair, and looking at the width rather than overall length:
You're doing pretty well at half the 5-6ft width/height.