Have recently replaced a Select Viper speed30 with a KA SL 30 fin - sailed it twice now on my s-type 93 and the difference was quite amazing. Felt much more solid and it didn't want to skip when tightly carving or spin out when heavily loading up. Another thing that it does is whistle at higher speeds (around 27kn +). I initially thought the boom or mast was the origin.

The noise is perfectly pitched and doesn't quaver and nor does the board - in fact when it's whistling the board feels very stable. Has / does this occur to many others and does it effect performance.