Anyway, about backbending: since I returned from Kino's LA workshop, I have been doing my best to incorporate certain things I learned about backbending into my backbending practice. There are a few things I learned at that workshop that are really relevant to me:
(1) Tilting the ASIS slightly forward and upward helps to achieve sacral nutation, which is very helpful for deep backbending. It is very difficult (maybe even impossible) to backbend deeply when your ASIS is tilted back: Try it if you don't believe this.
(2) Together with tilting the ASIS forward, gently rotating the thighs inward helps to secure a firm base/foundation from which the backbend can flower. Inward rotation of the thigh is not to be confused with squeezing the thighs together: They are two distinct and separate actions, and it is possible to squeeze the thighs till forever without ever getting the thighs to rotate inwards.
Based on this realization of the difference between thigh rotation and thigh squeezing, I have stopped using the block in backbends since I returned from Kino's workshop. As useful as the block may be for certain purposes, there is a tendency when using the block to focus more on keeping the block in place (and on squeezing the block to keep it in place) rather than on the inner-rotating action the block is supposed to help cultivate in the first place. This, I think, is one pitfall of using props in practice: There is always the tendency to focus on the prop itself than on the action the prop was supposed to help cultivate in the first place.
(3) It is also important to lift up into the backbend and allow the spine space to expand at the same time as you are trying to walk your hands deeper into the backbend. This applies mainly to Urdhva Dhanurasana, but it also applies to other deep backbends such as Kapotasana. Actually, Savannah over at Musings from the Yoga Mat explains this lifting and expanding action very well when she writes:
"For Urdhva Dhanurasana (backbend), Kino asked us to tilt the pelvis forward, lift the stomach and ribcage, roll the shoulder blades down and onto the back while allowing the entire body to assist in the arch."
The general idea is that when you lift and expand in the way described, you bring the entire front and back bodies to contribute to the work of the backbend, rather than simply letting the lumbar spine do all the work (resulting in lumbar compression, which is frequently painful). To show us how to coordinate this action with the breath, Kino had us tilt the pelvis forward, roll the shoulder blades down and bring the chest over the arms on the inhale in Urdhva Dhanuarasana, while walking the hands closer to the feet on the exhale. This same inhale-lift/expand-exhale-walk-forward action can also be applied to Kapotasana, even if the action is a little harder to replicate here because the fact that one is on one's knees gives one a little less room to expand outwards on the inhale. But it is doable, and it does create a good sensation of expansion in the spine; which, if nothing else, counteracts the I-am-feeling-so-claustrophobic-and-I-am-going-to-die feeling that one often feels in intense backbends.
Are all these things helping with my backbend practice thus far? I guess the answer is... slowly and in microscopic increments. To be honest, when I stood up from Urdhva Dhanurasana this morning, I found, to my horror, that my feet are still splaying out. But as I walked around campus later in the morning, I felt that pleasant aching feeling in my quads. Which I take as a sign that I am at least engaging the right muscles, even if these muscles have yet to become strong or long enough to prevent my feet from splaying out. I guess I'll keep working on this.