Average density ρ_surf in the outer 20% by radius (50% by mass) of bodies with diameter D grown at various accretion velocities, for composition A (upper panel) and composition B (lower panel), using the method described in Sect. 3.3.1. The curves can be compared to the bulk density ρ_bulk of 67P (red) and fragment density ρ_frag (thin black solid line) needed in combination with a 40% macroporosity to give ρ_bulk.