Another good lesson here...we're doing these in Tinkercad, and we started by creating the bottom of the box, then duplicating it, then scaling the duplicate/lid. My gut feel is that scaling the OD of the lid should scale proportionately the ID, so that it maintains the 2mm lip. Re-thinking, though, I'm guessing that scaling is increasing the thickness of the lip as well as the diameter of the hole and the exterior? Probably something very fundamental to an engineer, not quite as obvious to a liberal arts guy.