Wouter, combining several of your comments gives...
I'm still waiting for the guy who takes out a sheet of that strong farmers platic in a Hurrican Katrina like storm and shows us all how to better 50 knots with some 10 dollar hardware.
Windsurfer achieves his top speed in a hurricane like blow doing maybe 100 % or 140 % of the windspeed.
I remember Katrina posting winds of 175 mph. At 140% that has our farmer windsurfer pushing 245 mph!!
Great ride until you fall.