Have a look at some of the other videos earlier in this thread. The Norwegian guys on that foiled canoe show where the possibilities are for foiled downwinders. Also take a look at that French sailing team setting the speed record in their foiled machine.
Wow, have we got interesting times ahead - maybe the multihulled foil would be easier to control than a mono?
If anyone has tried normal "tow foiling" you will appreciate what an accomplishment this guy on the SUP has made. What he is doing is extremely difficult. Great stuff!