Make sure that the adhesive is compatible with the foam, some adhesives will disolve it. Before you glue it down make sure that you will have a bunch of weights that you put over the new plywood so that it bonds properly. I did a repair for a friend of mine a few years ago and we used a foam board adhesive. We were able to buy it in the tube form and by the bucket, we used a notched trowel to spread the glue, layed the plywood down and rolled it with an underlayment roller (its a heavy rolling pin about 60 lbs). We then layed pre-cut 2x6 over the floor and added weights on top of that until the glue dried, we waited 3 days. Good luck
2013 Prime Time 230 FBS
Days camped in 2013: April to November
Days camped in 2014...about 40
Days camped in 2015...more than 2014!!