well, that's just the thing... sector boards open up lower wind ranges.. I'm about 80kg and when in Europe I use Sector 52 as my light wind board with larger fin set... it is ton of fun to blast around in high speed, long distances, jumping on 9.5 when other kiters are staring at you from the shore..
Of course it is great in higher wind speeds, just faster...
For your use (15 knots and more in chop) 54 might feel a bit big and bouncy at first (S60 would be way too big for you). The board likes to be ridden fast, skimming tops of the chop. I found it lot easier to just go for it and when at speed, hang more of the kite and shift more weight from your feet into the harness. It's a blast
