[paulk]

If your boat is a 1934 motorsailor and you want to head upwind and not have too much leeway, starting the engine will probably be a lot cheaper and easier than deepening your keel by 25 cm by adding a shoe of some type to the keel. Adding that much wetted surface would likely slow down the boat a lot (perhaps by 2-or more knots?), to say nothing of the ability of the now elderly structure to support the weight and stresses involved. If you're not happy with the boat you have, perhaps you need a different boat. That's what the changes you're talking about seem to indicate.