Fluxes at 1.3 mm tor both observed Lupus disks with central star masses below 0.5 M_⊙ (purple), and RADMC-3D forward models (green) of our simulated pebble disks. Observed dust disk sizes in Lupus are categorized into three size groups: <5 au; either between 5 and 20 au or unresolved, and thus only constrained to be <20 au; and >20 au. The simulated disks show both the expected flux at sizes of 20 au, and 2-4 au for the dust masses listed in Table 1. The green arrow highlights the hypothetical evolutionary trajectory that dust in a disk would follow under the influence of radial drift, leading to more compact disks with lower flux densities.