Have skied the Whisper Fin a lot and it is something special. I have never felt a quicker turn with more acceleration off the apex. And yes, Whitney has been on it for quite a while now. Her 39's have never looked better. So has her Brother and Neilley Ross, along with some of the Big Dawgs.
It is different in that you can only tune it in 2 dimensions, Depth and DFT. The diffuser slots have to remain level at all times. It works best with your bindings forward and then you keep moving the fin forward and shallower to adjust for Smear, till you get it right where you want it. If you go to far, believe me you will know it, then back it off a little. It took me about 10 sets to find the sweet spot for my D3 NRG. I had a friend in another part of the Country that had one on his EVO, and after 10 sets on his, we both ended up with the same exact settings. I would be glad to share them with anyone that wants to know.
Right now I am back on the CG Fin, which is not as sensitive, while I work on New technique to match the performance gains from the new ZO Plus System. After I iron that out I plan to switch back to the Whisper Fin. Be advised, it also makes a loud whisle behind you. We nick named it the "Whisler Fin."