Great stuff Ronald, thanks for posting.

In that video (above) both foils seem to be fully extended at the same time, so I'm guessing they are separate pieces and one or the other (or both?) can be retracted independently? Or was that just the experimental phase and for the race they have a one piece foil?

The earlier drawing you posted made it look as if it were a one piece type where when one side is out, the other side is retracted, but the video has both out at the same time.

I was surprised when the announcer said it increases the speed by... 2 knots. I would have thought it would have been much more than just 2 knots.