It's behind a paywall

Edit: Reader view in Firefox steps around that.
fwiw, While not quite as elegant as this one, my Tillo foil had an integrated vertical fin on the top in 2018. Since it will be prone to getting scraped on the bottom and losing anodization, I wonder if it will be subject to more corrosion in saltwater environments? I would think the slender wing tips on the race wings, too, will require a lot of TLC in more hostile locations. The price one pays for being on the bleeding edge, I guess?