I personally would not worry about what you are describing. If you jack up one side of the rear axle, you will see that the torque tube moves to one side. That is because the geometry of the springs and shackles. The center of the spring will move as the spring lengthens and the shackle swings. When it is all together, this is not possible because it is constrained. I have used this technique on my 38 Master which is very similar.
