  We develop further the codim-2 future-past extremal surfaces stretching
between the future and past boundaries in de Sitter space, discussed in
previous work. We first make more elaborate the construction of such surfaces
anchored at more general subregions of the future boundary, and stretching to
equivalent subregions at the past boundary. These top-bottom symmetric
future-past extremal surfaces cannot penetrate beyond a certain limiting
surface in the Northern/Southern diamond regions: the boundary subregions
become the whole boundary for this limiting surface. For multiple disjoint
subregions, this construction leads to mutual information vanishing and strong
subadditivity being saturated. We then discuss an effective codim-1 envelope
surface arising from these codim-2 surfaces. This leads to analogs of the
entanglement wedge and subregion duality for these future-past extremal
surfaces in de Sitter space.
