It's sort of a patch for something that should have been mocked up and built properly the first time. I would always lock a frame down tight to the floor on screw-adjustable jack stands with frame straightening chain anchors and assemble the suspension without any springs, then move the suspension up and down with a jack. I could spot errors in wheel alignment or positioning of tie rods, etc. before getting the vehicle out on the road or the race track.
Your main concern with bump steer is going to be changes in toe as the suspension cycles through its full range of travel. That's easy to measure if you don't put the springs on top of the lower control arms, or at least use VERY weak springs and cycle the suspension through its range of motion. There's no substitute for doing it right the first time.
Jerry
