Actually I believe 'touchdown speed' is nominally Vref-5 although it is rare to see that flown correctly. Vref is the 'target speed' at 50' I believe?
bradlee - I am fairly new to winglets on the NG but I know nothing of this claim and I don't think that the winglets contribution to directional stability is significant. Perhaps CaptainSandL can help here? There is nothing I have seen from Boeing about it.