i replaced my w28 chain locker bulkhead. it was soft and channeled due to termite work. i chopped out all of the plywood, but retained the fiberglass tabbing on the hull. a replacement in one piece wouldn't fit through the companionway, so i had to make a scarf joint in the panel inside the boat. i modified the shape of the hatch to a trapizoid to provide more plywood at the sides of the hull. the hatchway is now wide at the top and narrow at the bottom. i coated both sides of the panel with three coast of epoxy with one layer of fiberglass on the chain side. . i epoxied the new plywood to the old tabbing and bolted it until cured. then i removed the bolts and laid a new fiberglass tabbing on the v-berth side of the bulkhead. then i refit the bolts.
i suggest that you carefully check your cutwater fitting (bracket that the bobtay attaches to) for corrosion while the bulkhead is out. it is much easier to replace without the bulkhead in the way. i replaced mine.
james