Hi Michael,
I have seen both references too. Below the navel, behind the navel. I think of it as an area, as opposed to a more limited, point. If you cut someone open and tried to find it, it would, of course, not be there. It is an energetic center in the energy body. I also envision a different place, when Master Lin says, at the end of a meditation, regarding placing the energy pill "deep" behind the navel. I experience more or deeper space in behind there! As you are focusing on the energy ball spinning faster and getting smaller, already in lower dan tien, this place deep behind the navel is somewhere else.Perhaps another dimensional opening, if that is the right word.. Does anyone ever see other energy pills stored there? It seems so to me , as a glimpse.. I feel an "area" as the lower dan tien. It would be hard to describe it, as how I feel it,,,,maybe small melon size, ?? sometimes bigger, sometimes smaller... In general it seems to occupy both areas below and behind the navel. As it exists, other dimensionally, perhaps the reference points mentioned, just get you there, as opposed to literally aligning with a single physical point in the physical body. When I concentrate there, my third eye/ inner vision seems to take over, which is a shift into a different reference of self. I know with other meditations/exercises, Master Lin refers us to areas, where as other methods I've seen mention specific points. Like bottom of the torso, versus huiyin point.