On instability topic, here are my practical tests to check yourself. Look in mirror - is your head slightly tilted to one side, is one shoulder higher than the other, if so is the hip higher on one side than other (put hands on hips), is one leg slightly shorter than other - get friend or family to help - wear flat shoes - lie flat- have companion put your heels together. If one heel is slightly shorter than other they can see that & tell you. If you have many of these characteristics this may suggest you have instability issue. Our brains keep our eyes even with the horizon & will alter body below in order to do that. Have a poster about this will try to post soon. D