TwinNDB,
The standard practice to which Centaurus refers in his opening post relates to the Boeing 737 recommendation to carry
(a) half the steady headwind component which is bleed off somewhere approaching the flare on the basis that this reflects the ground "boundary layer" velocity profile. .(b) the full gust value which is carried through the flare to protect against the random nature of gusts. .(c) a maximum additive of Vref+20