Michael Storer, and the people he got it from, for the inspiration.
My chief complaint of my pivoting kick-up rudders was the difficulty steering when it partially kicked up. I had a locking pin to use in known deep water but that is still not ideal. Shallow water control was impossible.
The cassette I built has an open back with two wraps of bungy cord. Initial sailing trials show it to be rock solid, but I have yet to see how it does over ten knots. At most, I'll have to add extra bungy.
Besides being able to set the rudder depth for good shallow water control, it also kicks up in either direction for those times when you have difficulty getting launched off a windy lee shore.