Boeing state that approach speed of Vref 30+5 or Vref 40+5 is flown in order that
full manoever protection is assured at Flap 15 (go-around) configuration.
Stall speeds are therefore considerably less than Vref 40-5 or Vref 30-5 (although I can't lay my hands on the factor above Vs for Flap 30 or 40 configuration at the appropriate flap Vref speed).
Touchdown technique is to effect touchdown at a speed between Vref and Vref-5 as previously mentioned (power being slowly retarded during the roundout/flare) - note that on a -800(NG) tailstrike will occur at around +13 deg pitch (oleos extended) or +11 deg pitch (oleos compressed).
Cheers
ScottyD
