I finally ordered a female pelvis model (http://www.universalmedicalinc.com/female-pelvic-model/detail/A61_9039) . I love this pelvis because unlike some of the resin models, it is moveable, just like your pelvis. Instead of simply reading about the cardinals movements, I am now able to recreate them, one by one, manipulating Khady's first doll through my plastic pelvis. In the middle of birthing an Occiput Posterior baby, wiggling the head side to side in an attempt to navigate the pelvis, I had a revelation. All moms should have the opportunity to manipulate a baby through a pelvis. It is a great hands-on a way to learn that position really does matter. Getting the baby doll out of the pelvis was also challenging when "mom" was lying down. In some positions baby counts on the flexibility of the tail-bone (yet how flexible is this bone when it is pressing into a hospital bed).
I think that if moms fully understood just how important being mobile is in birth, they might choose a birth environment that truly encouraged active birth. Books are great but there is nothing like hands-on learning.