RE: Isonic 111 speed
Sorry, I don't agree with Peter here but I think we are talking cross purposes. My experience is that the 36cm works absolutely fine in higher winds. I just need to work out when to start using it and I have a feeling that the 36 is actually better matched to the 7m sail than the 42.
Outright speed is affected by the size of the fin (but of course limited by the size (width) of the board). In 20 knots I can still hang on to my 7m with ease but the Is 111 with the 42 fin has become uncontrollable. To much lift means it starts to tail walk and in some cases literally takes off. The answer is to fin down, which is fine if you are looking for outright speed, because you are by definition sailing off the wind.
Anyway - the real question is whether the 42 stock fin is holding the board back? I still feel that it might.