ECU and CVC,
I do not really know what the MPBR is - with it dead on at 250 yards (that I am 100% positive of) I would think that out to 325 is a great estimate.
I would think that an aim and shoot philosophy with no hold over (out to 325 yards) would be appropriate knowing that I am on at 250.
I rarely worry about shooting low anyway... I always aim at the top of the deer, so a round that drifted low (assuming a broadside shot, which is not always the case) would simply fall down into the lower part of the shoulder and likely do bone / lung / heart damage.
I have never taken a deer out at 250 yards... we have shot opportunities that are that far, but I have never taken one.
With perfect conditions, which would have to include a rest on the stand or a good shooting stick - I would consider a 250 to 300 yard shot but the conditions would have to be perfect.
If I am ever presented with a trip out west, I would locate and use a 300 yard + range just so I could "know" exactly where the bullet was going to land.