Almost completely adrift of what Rob would be looking for, but centreboards have an asset in that as you haul them partially up the CLR moves af, which seems to be just the tweak once boat speed gets up

Sometimes it seems to me that what Rob has been doing is close to lee-boards, brings back memories of Herreshoff's Meadowlark.

Ok so heres my real thought, it is possible to run more than one board, The Lady Nelson (look her up) had lifting boards as she had to navigate shoals in her intended role to chart the Australian coast. Give some latitude you could have opposite facing centreboards, with a linkage rod so arranged that when one is hauled up the other goes down (under its own weight). Shorten the linkage rod and both boards will go up

But is it possible to have a rudder on the aft edge that works? My thinking is it would work, maybe not so efficient which my be a drawback on a hull with so limited rocker.

There might be another surprise there, as HP boards always seem surprisingly deep. Of course under the hull they cant ventilate the same and that will add some percentage of efficiency.