I wanted to ask about the LS-arch. Will the upper and midback affect the first pelvic tip efforts? If my upper and midback are locked (hinge or something), am I still able to tip the pelvis in isolation (and then it'd help the rest of the spine)? Are there any preliminaries that must be met, like a relaxed rear sacrum, and what if you have the 'no butt syndrome' (glute max is very short and hidden under a tucked pelvis)? I feel like the pelvis is also locked mechanically. One more important question is, what is the direction of the tipping movement? Is it ok to hurry progress by rocking on sitbones or by pushing a certain bone in a certain direction? Or is the tilt supposed to happen by itself? I can't get a picture whether the tail is to go down and back or just straight back from the L5.