On Feb 20, 11:56*pm, Jock Proudfoot wrote:
Anyone know in round numbers, what % increase in L/D garden-variety
winglets give?

It will always be a bit less than adding the same length in (equally
well designed) wingtip extensions instead.

You only go upwards if some external influence (class rules in gliders
and Americas Cup yachts, airport gate spacing in the 747-400) prevents
you from going sideways.