Probably important for handling characteristics to keep the recommended differential between front and rear. One of the reasons Corvairs got a reputation for such evil handling (aside from the Nader hatchet job that is) is because the Chevrolet said to fill the tires differently front and rear. Most people didn't. The Healey is the same, as it is "tail happy" and keeping the four pound differential with it (and the sway bar!) helps keep it in check. Those who use their cars in competition can fill us in better.