A lot depends of course on the weight of the rider. I think that medium and heavy weight riders generally need more boards.
I'm 87kg and would have a lot of problems planing with a 103L + 7.8 sail in 12 knots average. I would need at least 15 knots average. A bigger board would help and lower the minimum wind force again.
In 25 knots average, probably I would not dare to go on the water with a 103L and a 5.5 sail, unless it was a flat water speed spot. Probably I would use my 83L board with a 4.0 or 4.7 sail.
But probably you were not talking about average wind speeds.
IS87 / IS101 / RRD114 / US147
Last edited by BelSkorpio; 5th October 2012 at 06:10 PM.