Sailboats have centerboards so they are not pressed sideways for the forces of the sail. Some centerboards are weighted at the end. when the board is lowered the drop in the center of gravity enhances the stability of the boat. If you want to but a retracable skeg on your boat for tracking it can be done as described, WoodenBoat ran a article a while back showing exactly what you describe. You would need to have Nick tell you where to place it since it changes where the boat turns, same as on a sailboat. If you want to add stability either use outriggers, widen the craft, or use a ballast. Ballast is nice since after you have master the craft of balancing the craft by bracing with a paddle ( something I'm looking forward to learning myself ) you can remove the ballast.

Just some advice from someone building his first boat.