I've looked through my manual and there is nothing to say how you get it off!!!

Have you tried pouring water down the corners and seeing if it comes out under the car before attempting to pull it apart??

If they are blocked, I would try feedind some thin wire down them (just through the plastic holes) and seeing if that cleaned them out before dismantling.

Just looking at it suggests it would be a major PITA with lots to take off - but perhaps others have done it.

Cheers

__________________
1988 W126 420 SE

beware of fundamentalists!