The zero range for you crosshairs doesn't really matter, but if you play around you might find that a different zero range will give easier to remember holdovers for your other aimpoints.
Although I don't shoot much these days (even less since I broke my back) I do still get quite a few emails and PM's from people asking for advice and holdover charts etc.
Someone asked me for a holdover chart for their .22 the other day and after playing around in chairgun, I found that if they zeroed at 23yards, it meant that their 30,35,40,42 and 45 yard holdovers fell nicely into 1/2 mildot spacings (not exactly, but close enough).
Also, if you have a scope where you can't easily adjust the parallax, then my advice would be to zero at about 25 yards since that's going to be the range your parallax will probably need to be set at for best rangefinding in HFT.
It's best to zero at the range you're parallaxed to so that you eliminate parallax error when you zero.
I'm convinced that the cause of 'crossover' isn't anything to do with mounts being out of alignment - it's normally due to your eye being out of alignment and zeroing your rifle at a range your scope isn't focused to.