In this section, we extend our investigation by introducing a second BMC whose finite radius is explicitly taken into account, thereby moving beyond the point-particle approximation. To recap, we continue to work under a linear background concentration gradient ξ along the z axis, with a central "blocker" of radius 5R actively consuming substrate at flux J -. As in previous sections, this consumption produces a stagnation contour behind the blocker, which marks a balance between the background gradient and the consumption-induced gradients.