There are 3 generations of N20 rudders:

1) 1st gen, narrow blades
2) 2nd gen, fat blades that no one has great things to say
3) 3rd gen, properly designed fat blades. Also in use on the Infusion Mk1.

My boat had Phil's foils tuned 1st and 3rd generation rudder blades. We used the 3rd gen blades for most of our racing until one literally disappeared from the bottom of the transom down in the Tybee. Then we switched to the 1st gen blades, which worked fine for distance racing, no real ventilation/cavitation issues. We used them for 1 or 2 buoy racing deals afterwards, and I didn't really like them for that style racing-at slow speeds, aka on the start line in light air, they didn't have the authority I experienced with the Gen 3 blades and am used to on other boats (those monohulled things).

Keith, PM sent.