We discuss an extension of the venerable Parr-Pearson parabolic charge transfer model that explicitly includes 3rd order effects. We then use this new model to provide new arguments supporting the validity of Parr and Yang’s “|Δµ| big is good” (DMB) principle. Additionally, we show how to re-derive this principle from the Parr-Pearson parabolic model, using simpler arguments than those presented in our previous proof of the DMB rule.