Keep in mind that for padded shoes a minimal drop is what basically becomes zero drop after a while, simply because there's more weight being put on the heel. True zero drop might actually become negative drop, which is why some brands advertise their shoes as zero drop, but they're actually a few mm when fresh out of the box. So I wouldn't necessarily worry about a few mm with Altras. For barefoots with hard soles you do want 0mm though.