When I bought my '62 240D, the rear headliner was hanging very low, partialy blocking the back window. I pulled the rubbe weatherstrip at the rear doors, and the panels coverig the rear roof pillars to see and repair the problem. I discovered the rearmost metal bow that suspends the headliner had dropped because the rubber sockets that supported and tensioned the bow-ends into 1/2" holes in the inner roof had disintgrated. I made some metal sockets from heavy galvanised sheet steel that clipped into the roof holes for a permanent repair. My headliner has also separated where it was fastened under the rear window gasket, but the newly suspended rear bow solved the visibility problem enough that I haven't tried to tackle the rear window issue.
If you can't rig up something from scratch like I did, you might be able to find some 1/2" metal 'dummy-plugs at a hardware store or Radio-Shack, designed to plug unused holes in metal sinks, cabinets, etc... and drill appropriate holes in the dummy-plugs to fit the headliner bow.

Happy Motoring, Mark

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DrDKW