The difference with a powercat isn't so much the speed, but rather the directness of the course you are planning. No need to tack into a headwind and wind direction isn't critical unless its really blowing. And a ssuggestion I've mentioned here a few times: Run the powercat at a modest speed (I usually ran at 8-9 knots) and fuel consumption isn't bad at all. Just because it says the boat will run 15-20 knots doesn't mean you need to drive it that fast. Distances in BVI are all relatively short.