jp747,Shorter fin, come down to say a 27cm fin and see how it goes. You speed should improve
Hardie indicated a few months back. Get top quality fins, for two reasons, speed increase and safety (they dont tend to let go and blast you into the sail,mast,boom )
Followed his advise and it did for me (with a bit of far off coaching from firiebob)

hey guys..a 27cm hmmm the shortest i could borrow and try would be i think if i remember my sailmate saying a 28 i was thinking after the session if the tail was a bit bouncy then it must be the fin lifting the board, what if i rigged a bigger sail? or maybe that's about as fast as i get for given wind..i think it's a good fin a mfc the sl 07'model..but it was made for slalom pls. check out mauifincomp. and see what you think cuz it has like a freeride design to it..i was told by the dealer here that for real world sailing this should do it get out of the gybes quick and a bit of tracking unless it's always superwindy then go techto..i was all out today watching for debris and sand shoals and not holding back i was contemplating on rigging a 6.7 but a far distance from shore and trudging in the shallows, shucks i wish we had your conditions min and neb nothing beats a 5cm chop and 30kts. windanyways am all for just slalom, bump and jump but when it comes to leg stance do you as i most of the time bend my back leg at a say 60deg. angle and straight forward leg....you owziees got me hooked into going for speed and i never looked at a gadget most of the time i exited my gybe..maybe am trying to apply what you and gps team has and have the wrong equipment..firiebob sails his talk and i have no reason not too his grayer than i am