Best fit for the size distribution of the observed galaxies at z ~ 7 in the magnitude range 25.6 ≤ J ≤ 26.6 for the UDS field. Top: the cumulative distribution for the observed galaxy sizes (black histogram) is compared with the same for the simulated galaxies (blue curve), and a K-S p-value is computed. Bottom: the observed (black) and simulated histograms (blue), as described in the top panel, are compared with a Maximum Likelihood approach.