yeah 280cm 10cm over
another question: are both co-drivers seats flat-foldable or just middle one?[/quote]
On mine, neither fold fully forward like the rear seats do, but both fold back far enough for the headrest to touch the seat behind it. I've a fridge where the centre seat would be in `my' Multipla (sold) so I don't know if this seat is meant to fold fully forward. You've got to remember the Multipla front windscreen is quite steeply raked; go up more than a few centimeters and you'll not have the full 280 cm clear.
It's a long time since I've seen a surf board, let alone tried to ride one (if I want to get wet and bruised, I can always slip in the shower) but from memory, the front of the board is quite thin with a slight upward curve so upside down with the front on the dash should work. One way or another the thing should fit in (where have I heard that phrase before?), but you'll lose a lot of seat space doing it.