Re: "stance of heaven (and earth)" and IS
Think of someone that graps your wrist. Now the height at which you present your wrist is a major factor in how good you are able to divert imposed forces through your body (spine) to the ground. Many, many people present their wrist way to low, in which case the entire technique renders invalid (as aite no longer pushes forward, but downward). The next thing to consider is how your body is placed 'behind' your wrist. The contactpoint, your wrist, your center and ground contact are aligned such that you can indeed minimise torque 'spill'.
This off course won't work when you are rigid in either arms, spine, legs. Torque finds your weakest 'link' and overloads it easily, thus breaking your posture.
Hope this makes some sense. Pretty hard to describe properly.