Hi Donee -
The placement of the VG's was based on the PDF that trikkoncept linked. Have a look.
Flow typically separates at the trailing edge of the roof on 3-box vehicles, so that's where VG's would theoretically help most.
That said, also note that the Mistu engineers themselves managed only a 0.006 change in Cd in their application. So even if they were helping, I would have been surprised to see any significant change in the Corolla results.
Renault also used trailing roof edge VG's on their Michelin Challenge Bibendum Logan sedan:
http://forum.ecomodder.com/showthrea...179.html?t=179
It's quite possible that the Corolla's rear glass angle is already close to optimal, so wouldn't benefit much anyway. Tuft testing will help figure that out.