"size matters"

simple example: look @ the KONA races
EVERYONE has the same board
sail size you are allowed to use depends on your weight
trying to make it an even playing field
analyse wind n water and choose YOUR sail size
(
sometimes more kilos require more litres too)
in REALLY light wind there is often kite foiler with 20 meter kite and me on Mistral Equipe 2 XR carbon longboard with 8 or 10 meter sail - and NO ONE else
i am over 100 kilos
this one showing how weight affects sail size choice is from wikipedia: