I had my builder install the carbon ONNO skeg kit/system into the Guillemot Night Heron to help it track a bit tighter in winds and quarter beam seas. Therefore, I didn't experience the ease of installation that Wayne did - so can't comment on that.
What I can comment on is the fact that Patrick has designed what I consider to be the finest skeg anywhere. Very smooth deployment/retraction, makes a huge difference when the conditions get challenging, and man, what a fine looking design too. Patrick even when so far as to match the carbon cloth to the same weave that my builder was using too. Slick.
Agree with Wayne that I cannot detect when it is deployed - except in the fact it makes my boat track like it is on rails. Unlike the skeg on my Anas Acuta - this one doesn't slow me down a bit and I can keep it deployed and still keep up with my gal. (who paddles F-A-S-T)
This is a foam-core carbon fiber skeg, and carbon-glass cassette with a foil shape, rather than a flat piece of plastic or metal. Kit comes complete with all necessary parts.
Appearance: Unit is very solidly built, with obvious attention to detail. Skeg blade has a high gloss finish, with no bubbles, voids or other defects. I'm going to be devastated when I put the first scratch in it. Control cable is heavier gauge than any other system I've seen, and manufacturer says it will not kink.
Installation: As this was a retrofit to an existing skegless boat (1998 CD Caribou), it was slightly more difficult to install than on a boat under construction, but still simple to do. The cable suppied is more than long enough to give the installer a wide range of choices where to locate the skeg cassette and control slider. I chose to locate the skeg box about 10 inches further forward than is customary. It has no effect on function other than to keep the skeg in the water more in heavy seas. I also modified the cable housing attachment to the deck, using a bored out barbed pneumatic fitting and a hose clamp to anchor the housing rather than epoxying the housing to the slider unit. I also shaved down the slider ball some, and it is quite proud of the deck otherwise, and causes the cable to bow in the slider housing. I bought a Valley slider control and will try modifying that to fit, and see if it works any better. If not, I will fabricate a barrel style one out of maple dowel and a set screw.
Function: Wow! The slider ball works very smooth, and the kayak runs straight and true coasting with the skeg deployed. Weathercocking is completely eliminated in 25kt quatering winds with the skeg halfway deployed. Given that I put the skeg farther forward, when fully deployed, it does not cause the boat to leecock, however it does help tremendously with controlling broaching while surfing. There is little or no perceivable drag when the skeg is deployed, and it also does not give the feel of the skeg "taking control" of the kayak, as some OEM skegs do. It simply counteracts the kayak's tendency to weathercock, and assists in overall tracking. Unit does not leak.
Overall, an excellent skeg system. Highly recommended!