What's The Standard?

The most important thing in a handstand push up is that you finish the rep with your arms locked out, or does that not give you the whole picture?  That used to be the standard in CrossFit competitions - it was all about locking your arms out, but people started noticing there was an interesting thing happening with the hips (similar to the dip) where they weren't moving much.  Biomechanically this is how you measure the amount of work being done in a movement - the displacement of the center of mass.  So if some people weren't moving their hips and some were, while at the same time everyone was locking their arms out - this is not a fair standard.
You can see this in the handstand push up by the low back overextending at the top.  AND of course, improper form equals not full range of motion.  Focus on good movement, and everything else will take care of itself.  

Workout:

10 rounds:
1st minute:  Calorie row (12/15)
2nd minute: 5 handstand push up