The rear suspension has some "built in" negative camber from the factory that make the tires wear that way.
About the only thing you can do is rotate the rear tires from one side to the other. but the tire needs to be removed from the rim. Then you reinstall the outward facing sidewall, to the inside of opposite wheel.
I think Rudy is making some adjustable "Links" that will allow the rear suspension to be "aligned".