Washout will make the wing root stall before the wing tip. This will make the plane easier to fly - UPRIGHT. When inverted, the tip stall problem will be WORSE with built-in washout, and as mentioned in post #2, this type of aircraft can stall at any speed with enough elevator deflection.

It depends on what type of flying you are going to do with the Extra. It is designed to be symmetrical; to fly upright/inverted/knife edge without problems. Building in washout might ruin some of the flight characteristics when it comes to aerobatics. Outside loops, or negative G maneuvers in general, can be a problem.