Hard to tell from your photo, but the only ceiling mount looks like it is on the hallway section upstairs and one wall mount on the stairwell. Do you have the ceiling wired already for a centered larger scaled hanging light? Seems the space is needed something with some height and width. Could you post more photos?

more pictures

pictures

anyone have ideas on if the light should be center hall or both the hall and tairs

You need to have a light center hall and another once you get up the stairs.