Halting deads

Warm-up:
0.5 mi run

Crossfit WOD 083008
4x400 m runs (treadmill, incline=1.5, 1:1 work:rest)
1:38,1:34,1:32,1:31

3x3 Zercher squats (2x155,175)
4x2 halting deadlift (225, double overhand)

Runs felt great, and the heartrate hit 214 bpm on the last run! Played with 2 exercises I'd like to rotate in. Kept the weight light since I'm a bit fried from yesterday. The Zercher squats are nice, similar to front squats, although I felt it a bit more in my lower back. Halting deads (Rippetoe describes them here) are perfect for working the starting deadlift position, which has been causing me grief at the heavier weights.

Video of the third set of halting deads, with some analysis below.
The starting position looks good for the first rep, but I blow it for the third (and to a lesser degree the second) by setting my hips too low. Watch how my shoulders come forward on the third rep before the barbell moves vertically. You can see why this happens by comparing the images below:
In the first image, the dashed vertical line passes from the scapula directly through the barbell (or at least my best guess of where it is). This puts the shoulders in front of the bar, and produces a slight angle between the arms and vertical, just as Ripptoe argues is the correct starting position. In the second image, the hips are lower, pulling the scapula back, and the dashed vertical line is now roughly parallel to the arms. This causes the hips to rise faster than my shoulders when I start pulling, and they continue to do so until I achieve the position in the first image after which the barbell actually really starts to move. The difference between these two positions is pretty small (at least to me!), and they can be compared better when overlayed: