Pitlane Fanatic have a great little article on the diffusers that have been causing the consternation and (for the moment at least) have been deemed legal for Australia.

Who else thinks that the McLaren diffuser in that last picture is a sneaky "we’ll see if the others get through and if so take this cover off" version? Joe Saward certainly seems to think they have one ready at least. The mid-section looks a lot like the Brawn diffuser to me and surely you’d want maximum height there. So maybe Lewis won’t be scrapping for 15th like he expected.