Double-sided fireplace chimney

[rloverme]

I am designing a two-sided fireplace between a living and dining room, with a raised hearth for seating on the living room side, and an extended width to allow for wood storage (ie the shape of the fireplace surround will not just be a standard rectangle with a firebox in it). The fireplace will be in the middle of an open space, so not on a wall. Before I start building, I’m wondering if I should use interior walls at each floor to create the chimney chase, or if I should create one chimney chase on the first floor and set the height to extend through the upper floors and the roof? Also, I see tutorials that reference using various methods (interior walls, soffits, shapes) to create a chimney, and I’m unsure which is the best approach for this application. I don’t want to break anything on the upper floors / roofline that could become problematic if I move the fireplace later.