[aerohead]

I don't know the answer.The C-pillar winglets on the 599 race car helped with rear lift with no drag penalty.Their 'suctioned' diffuser DID reduce drag.
On the Fiorano,the aspirated C-pillars may accomplish the same thing as the race car.Not really a drag reduction per se,just not a drag penalty.
PS the development of the winglets required hundreds of hours of trial and error in the wind tunnel.At 200-hours,that might be $400,000 at Pininfarina.