No. There is no washout in an aerobatic model like an Extra. Thats not why I do it.

I shape the tips sharper to make them STALL faster than the root. The sharper angle of the leading edge at the tip will make the wingtip stall sooner.

You WANT an aerobatic plane to stall sometimes. You need the wing to stop flying in order to perform certain maneuvers--like snaps.

With a leading edge that is uniformly shaped and just gradually tapered--sometimes the wing will not want to stall for a VERY LONG time. When it finally DOES stall--it is very violent. It tends to make the plane twist up in a ball and go very deep into a snap or tumble.

With the sharply tapered tip--the wings will stall sooner--but less violently. You don't always WANT the most violent snaps that a plane will produce. This is especially true in IMAC or Pattern type flying. You want SMOOTH. Not erratic and violent.

It depends on the plane too. I have built enough kits and flown enough different types of airframes, that I kind of know how much to taper the leading edges. If this is your first big kit--you may want to just sand the leading edges uniformly. Have fun flying the plane and build a few more kits. Experiment slowly with the leading edge shapes and see how it effects different wings of different planes.