Smack and SailingDog,
While I personally believe that the JSD is a great device, and that a traditional chute is a bit binary (as Dog mentioned), there's no disputing that several people in several boats has had great success with both (and the opposite). Our biggest problem is probably that all the assumptions we've traditionally made when it comes to the sea, are basically skewed. "Engineers" typically laughed at sailors when they talked about freak waves, and showed them using their LINEAR models that it was impossible, however sattelites showed that they DO exist, and are more common than we could hope for. Also the life expectancy of large vessels were sometimes grossly wrong, again because the models we had were imprecise.
My point is that we're at a stage where we know that we don't know enough - there's so many parameters that we cannot simulate, nor test the possibilities, hence we must trust experience and our guts. We do have some empirical data, though, and the JSD/USCG testing is probably the best we have?
