While Prouts have done a fair share of offshore work that sounds quite narrow for a catamarran. The rule of thumb used to determine the minimum acceptable beam on a offshore Cat was that the beam is more than half of the length with 60% being more optimum. In capsize testing it was found that a near breaking wave height equal to the beam of a cat would capsize it with a high certainty of chance. The B/L=.5 is a pretty old ratios and I don''t know where the current crop of beam to length ratios have ended up but I suspect that they are wider still. .

Jeff