I 've got a mate Dave that is the specialist to get huge bubbles of delam.
He 's got a screw compulsive disorder.
Anyway his way, is to suck the skin back on by using a vacum pump.
Drill a couple of little holes near the bubble. Inject with epoxy (+ a bit of Qcell), put a sealed plastic on top of the area. Do the Vacum through the valve. Not too much as you might suck the resine into the foam, (but just enough to put the skin back on.
let the resine set with vacum pump on.
Done...Go sailing..
mm don't forget to pu tthe screw back on!!!!!