If you're going to use it primarily at FNS, I would probably zero your sights for around 25 yds. When you're target shooting during other range trips, you can take your time and judge wether to hold high or low. At FNS you've got to be quick, so I think you should minimize the number of things you have to think about. Just line up the sights and pull the trigger! I don't know what the average yardage is for the FNS stages, but I'm guessing around 25 yds. Nick would know better than I do I'm sure if you get a hold of him.
"When you carry a gun, a wacko with a tire iron seems much less scary." -Cru