I was at Waterfront park when Slingshot were working on the prototypes foils for retro fitting existing windsurfing boards (deep tuttle, powerbox). They said ball park would be around $900 US and will be ready to order in 2017 (aluminum not carbon).
It looked amazing and a lot of fun. The best guy sailing was the one with a specific board designed for the foil.
Windance also mentioned they would be sailing an affordable windfoil in the future.
I'm dissuade cause:
1. A wider board for best control and enjoyment (85 to 90cm).
2. Bottom shape rounded vs flat to distribute the force of a forward crash.
3. Strengthen area tuttle box.
Will a windfoil work on my board. Yes.
Will I have good control (58cm wide) No.
Will my board withstand the extra pressure of a foil on the front of a tuttle box. I guess not as the box was not constructed with that kind of pressure in mind. It will break sometime.
Will my body recover from crashes. Yes (but slowly).
Will my board/boom/mast recover from crashes. Maybe, most likely something will break.
Its best to buy the board and foil combo from JP/NP. Off course it'll be around $4000 US. Can't image how much a windfoil sail will cost! Off course they'll have a different boom and mast to match!
FYI: Northkites new foil design; it may work its way to a windsurfer too!
https://youtu.be/quNpSAt2JGo