Winged Keels Pros & Cons
I really doubt that adding unballasted wings would be worth the effort. Wings are very tricky to design. If they are going to really work they will also add drag and if not really well optomized this drag will quickly offset any real advantage of adding the wings. The reason that wings have been popularized is that in the normal forms that we see in production boats they are really a very specialized form of a bulb keel and the combination of an end plate and added ballast somewhat offsets the loss of efficiency inherent in a shoal draft keel.
If I were to build a set of wings they would have a plan form similar to a British Spitfire but with truncated tips. I would build them out closed cell foam such as a polyisocyanurate foam or a closed cell PVC with an epoxy/glass skin. For attachement I would make up a stainless steel weldment out of a stainless steel tube with a nut welded to the inside end and SS plate fins that would stabilize the foam. I would then drill through the bottom of the keel and using epoxy, glue in a piece of SS ''all thread. I would then turn the wings onto the all-thread and use glass to keep it from rotating. A better more secure way attach the wing would be to have two parrellel tubes that would end at each wing tip and would allow through bolting of the wings. Once thru bolted end to end the pockets would be glassed closed.
All of that said, the first time you run aground you will more than likely damage the wings and have to rebuild. In other words, with all due respect, I think that this is probably a really bad idea.