Nice insight Phil! Not sure about tiny increases in speed - as opposed to the traditional weighted center keel, probably quite a bit, all else being equal.
The interesting part to me is the foil shape of each being used to impart some directional righting force as well. If winter ever ends (repeat: EVER ENDS!) I want to dig a hole in my yard and look at how much the Mac's daggerboard actually moves about when fully extended. Judging by the slop I can see when fully retracted, my guess is quite a bit! Where the idea gets interesting is that if it was engineered up to the point of being a diving board - how much would that sharpen a/o improve the sailing qualities?
Taken one step further, like the puppies you outlined, what if you took advantage of the slop and put a very slight steer into it, depending on the tack, with some sort of cam mod? As long as you didn't act like a stalled rudder and cause too much drag, would a righting force result that would be similar in effect to one of those foils? I've got an unused, near new rack & pinion Mac steering package that would be perfect for handling the forces involved. I'd still settle for the diving board though..