I have come to prefer using the method of many FT shooters, by using the top of the trajectory curve as my POI, so there is never a need to hold under, always hold over, which I find easier. I start at around 15 yards, move out at 5 yard increments, and adjust my POI down each time I hit above my POA. Depending on the rifle, this usually results in a virtually flat trajectory in the 25 to 35 yard range (my most used), so a dead-on hold. For all ranges shorter or longer, it will be holdover by different amounts, but never hold under. With an air rifle's relatively loopy trajectory, a traditional zero procedure usually results in the need to hold under the target, sometimes by quite a lot, and often right in the rifle's most-used range. It's just my preference, but holding under has always been counter-intuitive for me, and more difficult to do consistently.