Gas Shock Problems on Outside Kitchen Door/Flap

I am guessing, because there is no real useful information given, that you are trying to anchor into a foam core. That's a losing proposition. In my Opinion, Until you either remove the foam core and replace it with something of substance, or somehow get to strong anchor points (i.e.: wood, fiberglass, HDPE), your spinning your wheels.

Carefully cut out a piece of the foam core and glue in a piece of plywood, then anchor to the plywood?