Our 73 trillium
has the same problem. I have used a spray-on adhesive for other projects on our boat and will be trying it on the ensolite next spring.
The cans of spray adhesive come with a long straw which is inserted in the spray nozzle, my plan is to just push this straw through the ensolite in several places and then spray the area that has come free.
This adhesive came as part of a kit for attaching insulation to fiberglass... which is used to insulate a boat motor compartment. It was purchased from Overtons.com.
I still need to find a place that sells the adhevise spray on its own as I don't want to purchase, and don't need the whole kit of insulation. Hope this helps in some small way and any other ideas would be appreciated.