For me Gary is abit hit and miss with his info, he does however suggest that the car is creating a stall somewhere, which I have suggested twice in 2 days on this thread, I'm not saying we're both right, it's just a thought.
Gary suggests that the Mclaren has an aggressive coke-bottle, I'm no technical director but I just can't see it myself.
Mclaren are 'convinced' that the 28 has more downforce than the 27 they just need to unlock it....
http://www.autosport.com/news/report.php/id/106141
Its reminding me this problemof the 2010 25, it had a massive double diffuser on which probably gave huge readings in the simulations but it needed a stiff platform and the lack of ride bounced the downforce off the car, not literally but you get what I mean