As near as poss the ball joints on the ends of the rack should intersect with the top and bottom wishbone fulcrum points. As suspension goes up and down there should in theory be no affect on the steering geometry.
http://t0.gstatic.com/images?q=tbn:A...5R94akKxHGBbEQ
By shoving the rack over you are in affect making one steering arm long and one short.
Bob