A friend of mine is the designer/owner of Falcon Sails. http://www.falconsails.com/ I can't say that kayak sailing is really my cup of tea, but the sails are definitely well made, and performance is quite good. I don't see that as much of a possibility with the "wind paddle" design. Don't take this as a sales pitch- I can just see a lot of ways for things to go wrong with that design. There isn't much control. But, whatever- thought I'd throw it out there in case you were interested.

m