I would like to know if anybody has tested the efficiency of inverted flight. For instance with a standard flying wing, would you get a lot less airtime out of the same battery flying inverted than doing the same flight upright?
Flying wings actually do not have that much different performance inverted to normal flight. Whilst there is normally more "Elevator" input to fly inverted the difference in actual drag figures is extremely minor.
I fly wings using flat bottom, symmetrical, semi symmetrical, and reflexed airfoils and none exhibits any significant performance difference when flying inverted.