I try to adjust the stancebar and the anchor point seems always to be in the middle. I played around with the "Anchor Point" and "Use Position Override" settings in ActionBars -> Stance Bar and it never seems to change anything.
If the stance bar is in the middle (and bottom) of the screen the position in the profile in the ElvUI.lua switches to "BOTTOM". If I pull the bar to the left side and set a value for x of eg 876, all is correct. In the mouseover the alignement changed back to BOTTOM (MIDDLE) and it seems to translate to the current position with the anchor in the middle. (But that is just in game, not in the lua file.)
Hopyfully it's somehow understandable. Sorry for my bad english!