Try this:

Drill holes all over the soft spot making sure you drill only the deck but not through the part hanging lose inside the hull.

Get a seringe from your local hardware store and a box of drywall screws and a cup of cooking oil.

Sounds kind of strange... I know

Mix your epoxy, load your seringe and start shooting inside your delamination throught the holes you drilled working in rows.

Grab your electric drill and work the screws all the way through your laminate after dipping them in oil. The screws will grab the lose part of the laminate, lift it and squeze it to the deck and push the exess resin out. You will waist some epoxy, be ready for spills, but you will add no weight to your hull and it will be as good as new.

After the epoxy has cured the screws will come out with little effort because of the oil.

Slap some filler in the screw holes, paint, go sail!

PS: check your drill bit when you drill the holes, if it comes out wet, you will probably have to cut port holes to allow the delamination to dry out, epoxy does not stick on wet foam.