Imagine a vertical plane that passes fore and aft through the center of flotation. The righting force of a weight is proportional to the distance it is from that plane. Unless you got her WAY over, the rail is further out from that plane than the tip of the keel. Rail meat is much more effective than keel weight if you sail her flat. On the other hand, if your worried about knock downs weight in the keel tip is the best place for it.
Math aside, I'd do the whole thing in lead if I could figure out a way that wouldn't cost a fortune and I was sure wouldn't fall off. Expect I'll end up doing something like Bill.
