I think that is what Gary was describing. He just pointed out that the keel winch doesn't really take the full 500 lb of keel, but only about 50% of that because is is supported on both ends.
NCC320, I like your idea of reinforcing with metal. I will repair the fiberglass then add a plate on top and bottom. Maybe an angle iron or two on the bottom.
I think the problem we have had with our keel is that we get lake weeds caught on the cable. When we raise the keel is is difficult to determine when the keel is up because is doesn't come to a hard stop, it just squishes the weeds. Next thing we know we are cranking on the winch too hard (crunch).