Funny you should ask, I just tried it, or at least the same idea, by tilting a rear seat forward to achieve the same thing. And guess what, it makes not the slightest difference

, so I'm afraid I don't buy into the story of the grill in the parcel shelf fix.
At least I don't have to be sorry that Stonk hasn't got the grill.
I don't think it's the vacuum effect holding the tailgate shut when you remote release, but rather its weight. The hydraulic lifts don't have enough mechanical advantage to raise the tailgate until it's opened a few inches. So when you pop the catch with the remote, technically it opens, but it just sits there and catches up again on the second stop as soon as you release the remote.
Why I wish this feature would work is because the tailgate gets so filthy under normal driving conditions. So when you turn up for an important business meeting you get your attache case out of the boot of your Cooper S and go give Bill Gates, Richard Branson, Ted Turner or whoever a roadgrime-filthy handshake.
