I am restoring a '79 Searay sundance given to me by a family menber to bring back to life. The back half is rotten and now gutted. we are replacing the transom wood and engine mounts, stringers along the gas tank, bulkeds. My question for the boat community is, Do I need to replace the 3/4 plywood stringer on the outboard side ( in the middle of the foam) it is only 4-5 " tall? or can I dig the rott out and pour in high density structural foam in ist place and set the new deck wood on that once it has been preped?