The foam is only there for padding and insulation and doesn't support the headliner. When the ends of the bow are inserted into holes in the rubber sockets, tension holds it up tight against the roof. Otherwise, there isn't anything in the center of the roof that supports the bow. Many cars used to hang the bows right into holes in the metal roof frame. Don't know why Mercedes felt they needed to add perishable rubber sockets, except maybe they thought there could be a noise problem
I made sheet-metal inserts to replace the damaged rubber sockets because this way I could fix the bow quickly, with something that would probably outlast the car.

Happy Motoring, Mark

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DrDKW