That's true about the solvation of styrene.
My concern was based on the "friablity" of the core bonding surface...certain types break down over time and any adhesion to the glass layer will be lost.
Epoxy, or polyester melts in a small degree the usual styrene type foams. Especially polyester resin. Epoxy only a very small degree. I think PU foam resists epoxy or polyester.
Not 100% sure, but you might want to check or test the foam you want to use first to see how it reacts to the resin. But polyester melts styrene based foams for sure.
If you want a good patch up job you should use specific foams for boatbuilding.
