This may not answer your question, but you might have a little laugh at my expense.
I had noticed that my boat was riding a little down at the stern. I couldn't figure out why she wasn't sitting properly on her lines. It seemed clear that there was too much weight at the stern.
I read in the manual that there were keel voids where prodigious amounts of water could collect. I convinced myself that there must be a keel void above the rudder shoe where tons of water had collected.
When the boat was on the hard I broke out my cordless drill. I drilled away into the keel about 12 inches above the rudder shoe. I stood back waiting for all that water to come streaming out............Nothing............Then I drilled another hole................
Nothing. There was a void but no water.
I hooked up a shop vac and stuck a tube in the hole. After two days of alternately pumping and sucking air I ended up with about two ounces of water for my trouble.
I had meant to pump in some urethane foam in there to fill the void but was so disgusted I just sealed the holes.
The next year I discovered why my boat was not riding evenly on her lines----the water tank at the bow of the boat was empty. Once I filled the water tank she sat perfectly.
I guess the moral of the story is the lesson I've learned several times--- If it aint broke don't break it.
If you're going to fill a keel void perhaps do it with something lighter than resin, which is going to weigh more than water anyway. Even better, leave it alone.
On the positive side, I did learn something by drilling into the keel. The fiberglass in the keel is over 1 1/2 inches thick. These suckers are built. They don't need any reinforcement.
Regards,
Peter