Jeff, what load did you use for the 802 yd shot? Was the hit right in the lungs or did you take out some bone?
Given my testing, I personally don't trust the X's to open up quickly at low velocity if you stick one right between the ribs.
In this test:
The "low velocity impact" X bullet on the left barely started expansion by the time it was stopped and left a very small wound channel. The Scirocco and AccuBond, however, opened up quickly.
Those are just my observations, but it is enough for me to favor plastic tipped bullets (or MK's, of course) for that type of shot. I'm interested in hearing more about your experiences with X's on the subject.