The Standard Keels are welded Steel plate, just a T shape, though a curved top to the keel to match the hull, mine had additional steel plates bolted to the sides to increase their ballast. People have had fin keels and drop keels designed for the Lysander, but they are really meant as a bilge keel boat.
Sadly I didn't build mine, as at the time I bought her, I was living in the Outer Hebridies, in Military accommodation. No facilities available, and the transport costs for materials to the Hebridies are expensive.