These foil windsurfers look very unstable along the longitudinal axis. Maybe the centre of lift is too far from the centre of gravity? This does not seem the case with the yachts as they look well balanced. They also use multi-hulls for stabilty. To me these "foil windsurfers" look a bit like a toy pony on a merry-go -round!
If it is light there is not much chop so you don't need to be above the surface as it is smooth. The windsurfer in the clip is flying past the "foil windsurfer". So it may be better to just have a better/bigger engine? i.e. Better sail technology as discussed in other threads for light winds may be one way to go? Or a look at better foil design specifically for the windsurfer?