I haven't done that repair but I would guess that a heavy duty impact adhesive (Evil Stink?) would do the trick. Coat both surfaces, allow it go tacky then carefully bring them together.

Hi Phil and welcome to Eribafolk
This problem has arisen on a number of occasions and this is what we have sort of established.

Firstly, please read this thread:- Pop Up Roof Issue on My Bali

What is apparent is that 80s Eribas had a different way of fixing the roof lining to 90s Eribas and we think the modification of using a larger unequal angle from 90s models onwards was because of a fault that was manifesting itself on Early Eribas.
As you can see, the unequal angle also clamps the top rail of the canvas down which in turn is fixed to the headlining.

Most people with the problem you are seeing have managed to fix it by taking the roof off and re-gluing the roof components together. Not sure which glue they used but there is much talk about Gorilla glue at the moment.

One owner took his roof to a garage or boatbuilder who worked with fibreglass every day and got them to re-stick the roof.

Randa