On another forum it was noted that your gun's POI vs. POA when shooting at 25 yds. can be off by about 8" vertically. This is assuming you zero your gun in pretty close, e.g. ~7 yds. That's not acceptable to me. [Caveat: I can not verify these claims].
The factory chose zero at 50', apparently for a reason. Other posters on that thread insist to zero in at 25 yds. and that way you will not be off more than an inch or two from a few feet away out to 25 yds, and beyond, to about 35 yards.
And yet another alternative is not to correct for parallax by sighting the beam parallel to the bore at all times-this way you're only off an inch or so high and maybe a half-inch to the left.
I'm getting my CT's in a couple of days from Midway, and think that I'll zero them in to 50' as recommended and apparently preset by the factory. It may be a PITA for me to try to see and zero the target clearly enough at 25 yds, so 17 or 18 yards (~50') should do, unless I use a large target.