most folks have tight lower back. by "tucking the tail bone", it stretched the lower back, the area opposite of your hara, methink the chinese called it mingmen (gate of life?), and relax it somewhat. you can rotate your hips back and forth (don't do in-front of member of opposite sex, too suggestive for that
) there is a point where your entire body seemed to sat on top of your leg/hips bone/joints (kinda hard to describe) so that your shoulders feel like they sat on top of your feet. in that place, the power from your shoulders can pass to the ground and vice versa. what received send. hmmm gate of life, tightness = gate closed, i.e. no energy flow. by bringing the shoulders into the spine, energy flow unobtrusively from finger tips to feet, providing that you are not tensing up various places around your body. weak conduit points are hip joints, shoulder joints, ankle joints, wrists. most folks have strong muscles, but weak around the joints, thus unconsciously tighten muscle around the joints to compensate and ended up blocking the flow.
just some of my random thoughts. probably won't worth much. wonder if i could trade for a hotdog and a drink.