[R129 SL] 129 headliner sagging

[Tom and Karen]

Dear listers,

The headliner in my 1990 sl has become unglued and is sagging. I believe 
it is due to the deterioration of the foam insulation layer to which it 
is/was glued and perhaps also because the vinyl appears to have shrunk.
My first thought was to try to reattach it use the type of spray 
adhesive I used when repairing the hood pad, but I don't think it will 
bond to the foam insulation layer.
Has anyone else had experience with this problem?

Tom
1990 500SL
1988 300E
Fort Collins, CO