I don’t want to retract EVERYTHING I said, but 6 months later and 1 narrower home-made barracuda style board 30 SUP foil sessions learning to ride the 21" wide board with 10 more pure downwind sessions ranging from bay runs with 30 mph winds, to bay runs with 40 mph winds gusting to 60 mph, to multiple ocean runs with everything from ‘moderate success’ to TOTAL SKUNKINGS, beatings, drubbings and miles long paddles . . . .
IF you can find the perfect downwind playground, like I showed above from Coyote Point to 3rd Avenue in San Francisco, 20 knots of wind just after high tide - THEN it can be easy. Otherwise LOOKOUT!!!
This guy has the best perspective on learning the sport of Downwinding that I have seen yet.