which adhesive for XPS backed plaster board

What is the best way to stick this stuff to my wall where I can't reliably screw? I want a proper tight bond, without melting the polystyrene.

It's only for one small piece around my window, where I can't screw half of it because of the lintel placement.

The Knauf guidance recommends their direct bond plasterboard adhesive to dot-dab, but I need to keep things as thin as possible (it's 27mm xps board, and I need it to rest above the window and not hang down below the window frame)

cheers

whitling2k

 

Thanks - looks just the job