Back when dinosaurs roamed the earth there were a couple folks on this list who had roll tanks designed for their boats. If memory serves, at least one of them did a Hawaii trip, maybe two. They sounded VERY effective although my takeaway was that they needed to be professionally designed. It didn’t sound like the build was a big deal. Unfortunately memory doesn’t serve very well and I can’t remember their names. Maybe Bob Phillips from Tortola? Regards, Randy Pickelmann Cool Change-lying Rockland, ME