The aft chain plates on my Columbia 10.7 had a problem; the tabbing on the hanging locker had broken, allowing the shroud to poll up the chain plate and crack the deck. That allowed water to leak into the deck core, weakening it.
I used a 24" length of 1-1.2" x 1-1/2" sainless steel angle underneath the stringer. The forged eye bolt passed through this angle. I also filled in either side of the eyebolt with wooden filler blocks, then laminated 6 layers of fiberglass cloth and epoxy. The fiberglass strips went down the hull, scross the top of the stringer and then down the wood blocks and hull underneath the stringer.
A view from above the stringer.
The new chain plate in place. This chain plate extends below the locker to connect to the cable stay.
A view from below the locker showing the cable connected to the new chain plate.
A view showing the cable stay connected to the eyebolt and chain plate.
The finished installation. A very minor cut will need to be made to the edge of the berth cushion.