Great posts Bryce. Really brilliant.
During this thread, I've been wondering of you could tie an anchor to a pair of 60 foot lines, suspended from each midship cleats, to act as sort of an underwater mast when anchored. The weight of the anchor keeping the lines taught, combined with the angle of the lines would provide increased rotational inertia, especially for low angles of motion. There would be some additional dampening added by the anchor in the water (which I'm visualizing would keep the anchor from enscribing perfect arcs during rolling).
And the lower center of gravity of this "mast" wouldn't make for increased roll amplitude due to top-heaviness.
There is a common trick I think they call it the flopper stopper or some such. You can make your own and they have commercial units.
It is basicaly a bucket with a bottom with a one way flap. The bucket sinks easily as the flap opens inward but when you try to lift the bucket the flap seals and it is hard to lift.
The bucked is suspected by a line from a boom which is set off the beam of the boat.
Supposed to work pretty well.