thanks.
as luck would have it, I will probably be pulling the motor this winter anyway to fix an oil leak, so access might not be a problem.

What is involved with removing the balsa core? I am envisioning grinding away at the hull, and that scares the crap outta me.

Cut out top layer of glass using a hole saw witout an arbor bit (or a very short one). Use a razor blade/scraper and sand paper to remove balsa.