Keel stepped mast
If you plan to change from a deck stepped mast to a keel stepped mast, you need to do additional redesign. The big difference is that in the deck stepped mast, the deck is trapped between the compression post from below and the mast from the top. If you cut a hole in the deck for a keel stepped mast, the deck will rise as you tension the standing rigging and the sides of the hull will be pulled closer together (collapse) as the deck rises. This is not good. Many keel stepped mast designs make use of a tension rod that is fastened to the keel near the mast step and the other end is fastened to the deck to keep it from rising. This could be a major redesign, since the load from the tension rod can be significant. You would have to design a load distribution plate around the hole in the deck, so the tension rod wouldn't just pull through when it tensions up under load. Good luck on your rebuilding project.
