Drawing the same pose at different speeds seems like a really good idea (one I should probably implement) though one thing I noticed is that you seem to be starting with the longest time and doing it progressively quicker (I'm just guessing based on it going left-to-right). I'm wondering if it might also be useful to tackle it from the other direction, so that you're building up to the longer drawing rather than breaking it down?
looks pretty damn good to me. i dont know the posture you copied however. seems like you understand the upper lower twists, and the proportion are good, also the gestures are alive, so that's all good.
now see if you can draw at this level from imagination :) that's your real test.