Just to explain, if you run toe-out up front and zero toe in the rear, then the car will "hunt" all over the lane while you try to drive in a straight line on the street. So you need a little rear toe-in to help the car stay straight, even though it will still be very sensitive to inputs with toe-out up front.
Look up Ackerman Steering... it has to do with the axis of rotation of all four wheels around a central point. To be brief, when you toe-out the front wheels just the right amount for the wheelbase of the car, then your front wheels will scribe perfect arcs around any turn (disregarding slip). Ford has published the figures in the manual for wheel alignment of the SVT, at least for the front... the rears are a different story.
If you want the car to track well on the street (using stock components), you should set Ford's minimum rear toe-in setting, that way you should be okay on a circuit and on the street. If you want to track-dedicate your car, then use zero rear toe, along with Ford's toe-out setting up front... just be prepared to suffer over every bump on the way to the track, or trailer it.