Despite the loss curves being modulated by the APL, the density profiles also play an important role during the optimization. The density profiles computed in epoch 0, i.e., using the initial set of parameters, and epoch 600 are shown in Fig. . We observe a systematic improvement of the density profiles for all the phospholipids, being able to reproduce in most cases peak positions, water penetration, and even structuring of the alkyl tails as seen, e.g., for DOPC, DOPE, and POPE. The robustness of these results finite sampling time and simulation size is supported by the nearly identical density profiles Fig. of the Supporting Information for four times as large system simulated over 50 ns. For the DM and DP series, even with the improvements brought by the optimization, we observe that the intricacies of the alkyl density profile were not perfectly reproduced. We attribute this to the fixed topology adopted during the optimization, with bond and angle parameters not being optimized. As shown in previous studies, optimizing the bonded parameters can greatly improve the description of coarse-grained potentials. However, in this work, we focus on optimizing transferable nonbonded parameters (which were kept constant in Ref. ) and leave refinements of topology and bonded parameters to future work.