This may have been discussed already.
I've been pondering what is the best "zero distance" for close-range hunting with the Tac15.
The following chart is the Ballistics for a 425gr Tac15 arrow shot at 400 fps.
I computed it using a ballistics calculator found here: Handloads.Com Ballistic Calculator
The BC of a Tac15 arrow is 0.06. This BC was computed from measurements by someone on this site who was brave enough to shoot through their chrony at 0 yards (400 fps) and 100 yards (332 fps). I forget who did that. Might have been xbow775.
Anyhoo... the vertical axis is inches and the horizontal axis is yards.
If you zero for 20 yards to get the blue curve - nice and flat, within an inch, from 3 to 25 yards,
If you zero for 30 yards you're within 2 inches from zero to 35 yards.
If you zero for 40 yards you have to tolerate being 4" high at 20, but it's within 4" of flat from 0 to 47 yards. This might be a reasonable zero for elk. (I've never hunted elk).
So based on this, if you don't want to mess with ranging deer inside 35 yards, zero for 30 yards and sling away!
My mil-dot scope is zeroed for 20 yards, but the next dot down (at 4X magnification) is 30 yards. I generally leave the scope on 4X all the time.
So an easy and quick strategy in the tree-stand would be for me to use the crosshair when the deer is 'close' and use the first mil-dot below the crosshair for shots 'a little farther away.'
For shots "waaaaaay out there' I've gotta dig out the range finder.