It needs to be parallel to the inclined plane through the centerline of the axles. With the panhard as it is now, it looks like you will have rear roll steer, rear bump steer, and possibly binding at some points of suspension travel. The three link creates an inclined vertical plane through the axle housing which controls the fore/aft axle position. The panhard as it is will try to control both the side to side axle position, and the fore/aft axle position, which may cause some binding in the range of axle motion.

Have you tried to swing the rear axle through it's range of motion yet?