Sorry, but that looks to me much too much like an Air Brake - and worse it will probably create a vacuum turbulance behind the car - by pushing air up.
Not a fan of the deleted lower indicator etc lights, and not sure what to make of the taller, blunter and seemingly less aerodynamic front end.
Also seems to have a larger Windscreen glass area from the slightly raised roof and lowered belt-line / Firewall.
Thanks for the great work Chazceron, and your well considered attempt to produce a genuine NON-Idealized render, reflecting as realistic a representation of the S650 as permitted from the very limited imagery available. I usually cant be bothered looking at other Renderers, as they usually...