All the new cars have incorporated designs to maximise the double diffuser concept as best they can, but while some look relatively simple - such as Sauber's relatively basic back end - others are pushing the window to its limits.
The double diffuser has been banned from 2011, but because of the fundamental influence of its design on car layout, once it was declared legal early last season it became the basis of all early conceptual design work for 2010.
The Overtaking Working Group's plan to improve the show by making diffusers smaller was the right one, but because the law was ambiguous it was sidestepped by the double diffuser concept.
The FIA perhaps should have immediately declared it legal for 2009 but banned it as of 2010 - but teams were already well into their conceptual planning so the only solution was to stop it in 2011. So, for this season, it seems their decision has opened the floodgates.
Ferrari have already made calls for clarification this year because of fears that designs could be pushing the boundaries again, but Sam Michael, whose Williams team was one of those that pioneered the design at the start of last year, thinks not. He has claimed that once the decision is made on an interpretation, the limit of that interpretation has no bounds.
If this is right, then, there is an open playing field when it comes to the diffuser - but where as the most effective strakes, flick-ups and even wing and endplate designs can be quickly copied, the diffuser is something that is deep rooted in the concept of the car - and again, it will be those teams that have pushed the boundaries hard that will benefit for 2010.
McLaren's diffuser design is an all-out solution that appears highly complex and takes the double diffuser concept to a whole new level. Beneath the lower section, there are multiple vanes and strakes to steer air in the right direction and maximise the effect of the underside, while in the upper section the diffuser area feeds right up to the underside of the rear wing's lower plane, creating a massive exit area which will significantly speed up air under the car and increase the downforce gained from the floor.
So what of Newey?
Last year, his team missed a trick with the double diffuser. They caught up, but because the layout of the car did not suit the double diffuser design they could not exploit it to the maximum. This year, the area has been flagged up and the green light is on for innovation - and there are few better at exploring the loopholes and maximising opportunities than Newey.
Charlie Whiting has been busy over the winter fielding questions on design interpretation from a number of teams, as he was last year, and his vetting process proved right on the diffuser argument last year.
Brawn admitted that Newey, his long-standing closest design rival, thinks "pretty laterally" and hinted at the possibility of something that "we don't know about" appearing on his car.
But given the arguments last year, surely Newey will have taken a cautious approach on any designs that came close to what he saw as the edge of the boundary. Expect instead to see an extreme McLaren-style diffuser, but one that does not go beyond those limits.
- Adrian Newey