We have used this design and train cycle to answer a number of fundamental questions about force field design protocols. It was shown that the details of the underlying QM method and implicit solvent model have negligible effect on the accuracy of condensed phase modelling with the designed force fields. That is not to say that any set of charges gives identical results, but rather that as long as the charges and Lennard-Jones parameters are co-optimised, the overall accuracy of the force field is insensitive to the particular choice of model. In this case, future efforts should focus on the cheapest QM methods that continue to give reliable results. It is well known that there is no unique method to partition the total molecular electron density into atom-centred basins. We have therefore investigated two variants of the DDEC AIM method, and the MBIS approach. Surprisingly, the older DDEC3 method showed improvements over DDEC6, but given the improvements in the latter in robustness and transferability of the charges, we continue to use this approach.