I'm not sure what the correct adhesive is, but I would not recommend Gorilla glue. Gorilla glue doesn't contain solvents that would dissolve the foam, but it is a urethane adhesive that reacts with moisture in the air to cure. During the cure process, the Gorilla glue will turn a lighter color because it will actually begin to foam. The foaming causes the glue to swell, which makes a nice, strong joint if the joint is clamped tightly. If the joint is not perfectly clamped (highly unlikely in a large, flat area of a wall), the swelling of the glue will leave the exterior fiberglass skin bulged and uneven.
I tried a similar repair under the rubber roof of our old travel trailer where a radio antenna was mounted. I removed the antenna and shot a similar glue (different brand name) under the loose rubber of the roof (about 8" diameter) and put a board with a heavy weight on top. After the glue cured, I was left with a bulge in the roof; but at least the rubber was sealed again, and no one could see the bulge from te ground.
Epoxy may work, especially if it's low viscosity that you could get to flow into the joint and cover most of the delaminated area. Epoxy usually doesn't contain solvents that would cause the foam to dissolve.
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