Here's another suggestion....

Drill a 1/4" hole directly through your outer stem into the end pour. Drill deep enough to reach the void that the water created and allow to dry completely. Seal the existing rope holes from the outside with painters tape and stand the boat on end next to a deck high enough off the ground for you to inject an epoxy mix through the hole in the outer stem and fill up the void. After it cures, epoxy a 1/4" dowel of the same wood you used for your stems into the 1/4" hole you drilled, sand and apply glass tape patch over the stems to seal.

If you didn't add outer stems to the S&G hull, you might accomplish the same using a smaller bit and drill through the epoxy that joins the hull panels together right under the tip of the bow and stern. You could easily re-fill the hole in the seam with epoxy after filling the voids in the end pours.

Bob