Interesting following the recent post. My CFD suggested minimal if any gains.... however they did have an aggressive upper element profile. Sauber tried something similar during testing for their last season, and left it there! Although the profile and element shape in general for the Mclaren seems much more complex.
I guess if its been developed they must predict some substancial gains.... I would tend to agree with scarbs looking at the profile, the central section appears to be to clean up flow, whereas the outer ends may produce some downforce.... I guess testing will show whether its effective or not. If it is I hope it stays, although i expect it to be banned.
MrT