I've rode a hydrofoil on an air chair, and on a tow surf board. It is a very surreal feeling, almost as if you are flying. Choppy water has no effect on your stability, as long as your foil doesn't pop out of the water. When that happens you tend to fall pretty hard. I wonder how the sailors are able to control the use of the foil. If one of the foils was to pop out of the water, hold on.
I remember my first time on an air chair. It's a surreal experience, for sure. One thing that few people appreciate is the effect of noise on your experience. With an air chair, you've got the noise of the motor boat in front of you, but you're at the end of a ski rope that is 50-75 feet long, so you've got some distance. When you go up on the foil, it's striking how much less noise there is than when you're on skis or a wakeboard.
I remember having a similar feeling the first time I sailed versus riding in a motorboat. The lack of engine noise makes the experience of sailing one of the most relaxing and exhilarating activities at the same time. I can only imagine what it's like on a hydrofoil sailboat. The quote from one of the cat captains at 2:34 sums it up really nicely: "Yes, it's crazy, it's noiseless, fast, and it never ends." I find it interesting that noiseless was the first concrete adjective he used to describe the experience.
All boats perform poorly when the weather is really rough. The degree to which they can remain seaworthy in inclement weather depends on design decisions.
A hydrofoil design actually does really well in choppy waters, because you elevate the hull out of the waves. The lift generated by the foil happens below the waterline, so you don't feel the surface waves. Just how large a wave you can negotiate with a vessel like this depends on the elevation provided by the foil design and your stomach for hard landings.
All in all, if you were to take the foils off this boat, I'd venture it would handle worse in the same waters as the foiled boat.
Sidenote: Also, FWIW, I didn't downvote you; I dropped you an upvote, because I can see why someone might think this way.
