Ratio between source size measurement and true size for ten simulations of microcaustic networks with lensing properties corresponding to quasar image A of J1131. Using L/L_E = 1.0, 0.1, and 0.01 for three assumed luminosities, the source size corresponds to R_λ0 = 0.277, 0.129, and 0.060 light-day, respectively (see Eq. (2)). The unbiased measurements are labeled as black lines for reference purposes. Each time, three typical IMFs are implemented and labeled in the top right corner. The results are clearly insensitive to the choice of the lens galaxy IMF.