This day was not my lucky day, again the predictions showed wrong and I brought the wrong sail with me. The ssw wind went from nothing to overpowering gusts in a few seconds and back, so hardly sailable with 8,5m2. Up on the water, the wind was a little more stable, but too strong so I quit after a few km's.
I didn't even think of doing the "speed" thing, better luck next time. My lesson learned: always take all of your gear with you...