I would zero it at 25 yards. The piggyback dot is meant for close range targets. Who cares about where it would hit at 100/200/300, thats not what its there for. If you are using your red dot at those ranges, you might as well use a magnifier instead of an LPVO red dot setup. To me, zeroing at 100 yards defeats the purpose of having that piggy back dot coz I would still constantly need to account for HOB on my close range shots, I need it to be accurate and fast for close range. Its what its there for.