just a note,
Big part of the 5% gain doesnt come from the winglet itself.
The winglet reduces aerodynamic burn with around 2-3% compared to
an acf without winglets at the SAME weight.
However, an acf with winglets can plan less trip fuel than the
one without, so if the two acf fly the same route, the one with
winglets will ALWAYS be lighter than the one without which
makes the total gain 4-5%.
XPM