Moving beyond z = 0, the velocity becomes positive and eventually decays, but the curves reflect distinct pathways through which the test particle crosses the transition region influenced by both the blocker and the second BMC. In general, a larger second BMC more strongly perturbs the gradient: it can block or redirect flux lines around its finite surface, leading to modest differences in the velocity profile relative to smaller-radius cases. The net effect is that explicit particle sizes add another layer of crowding complexity, exemplifying how intracellular structures of varying radii can jointly dictate the directions and magnitudes of diffusiophoretic transport under simultaneous background gradient and consumption.