It still exhibits the "flop roll" at 45 degrees to the seas -- as the boat turned in the video, just for a second.
There is a reason for this that goes beyond ama location. In control system theory, your "flop roll" is referred to as "roll coupling." The problem is that the very long vaka (main hull) has tremendous longitudinal stabilty, and the configuration of small amas (the outer hulls) has little lateral stability. Therefore, when the boat wants to pitch, its easier to dissipate the energy by rolling than by pitching.
The US Navy is seeing the same roll coupling in its large Littoral ship with similar configuration.
The way to solve this problem is through active controls. Like the stabilizers needed for non-planing powerboats. However, you could go with something very efficient.
Consider experimenting with Moth foils mounted on your amas.
This is a long video, but you can see clearly the wand mechanism on the bow that adjusts the angle of attack of the main foil. The angle of attack of the aft foil is done by the skipper twisting the tiller extension. http://www.youtube.com/watch?v=QMsM4TG2ce4