Hey, if you guys haven't replaced your little clips on your windscreen and your car is three or four years old, this is just about the best use of $5 you will ever spend on your Boxster.
I ordered them and popped them in last night and the center windscreen NO LONGER RATTLES.
Oh happy day!
Even if the clips are not broken, they stretch out and will wiggle a little back and forth and this is what causes a lot of the racket when you are driving on the freeway top down. Replacing them eliminates the wiggle room.