With crow mode fully deployed, you are creating a ton of drag... and have killed the lift at the outer part of the wings. It sure isn't going to hold altitude without adding a bunch of power and pointing the nose up...

I think its a matter of how much you are deflecting the surfaces... I generally think of crow as full deflection for the huge airbrake effect. Very useful to put a floaty glider down for a spot landing. I hadn't really considered thier use on a high speed heavy aircraft to make the landing slower before. (and the gliders don't have power to keep altitude with the things deployed...)