Here is another project to consume time and bucks and keep you dockside a goos bit longer.
From, Boat design net
There are a bunch of variations on Frahm Anti-Rolling Tanks. The U shape is one, another system is tanks open to the sea and cross connected, a modern variation is the Flume tank. http://pws.prserv.net/flume/flumetankstabilizers.htm
One example of the Flume Tank that apparently works was designed by Professor Don Bass of St. John's Newfoundland. This tank was mounted on a motoryacht called Swan Song, a Roughwater 58' designed by Edwin Monk. The rectangular tank is on top of the pilothouse, and is 12' long (athwartships), 4' fore and aft, and 16" high. Inside are 5 T-shaped baffles !8" from either end. The tank reportedly weighs 250 pounds (foam-cored glass) and has 1550 pounds of water in it, about 6.5" deep when floating level. The owner it totally tickled with it. Zero maintenance, zero drag, but of course real concern about high-angle stability and a simple system to dump the weight if needed.