Now, what happens if we impose c2ab=c2ss , i.e., a simple double hybrid rather than a DSD or DOD form? (As always, parameters are re-optimized self-consistently.) The results can be found in Figure and Table in the Supporting Information. Even at cX,HF=0.75 we find a shallow WTMAD2 reduction (0.04 kcal/mol) at κmin; as cX,HF is decreased, this 'well' is deepened until it reaches 0.36 kcal/mol at cX,HF=0.50. (κmin decreases in tandem with decreasing cX,HF.) Among the five major subsets, at low cX,HF the WTMAD2 component from noncovalent interactions (NCI) decreases as κmin decreases, while this is detrimental to small-molecule thermochemistry and (at κmin =1.1 to 1.45) for barrier heights as well: the former tendency grows weaker, and the latter stronger, as cX,HF is increased. We note that the ωB97M(2) combinatorially optimized range separated double hybrid of Mardirossian and Head-Gordon 40 has c2ab=c2ss and might hence benefit. (The way spin-component-scaled MP2 behaves differently from standard MP2 has been rationalized to some degree as approximate higher-order effects. Interestingly, the behavior seen for the κDODX-PBEP86-D3BJ functionals (i.e., where c2ss=0) is fairly similar, with lower percentages of HF exchange significant benefiting from PT2 regularization. For example, the WTMAD2 'well' for κDOD50-PBEP86-D3BJ is 0.39 kcal/mol, but for κDOD63-PBEP86-D3BJ, this shrinks to just 0.04 kcal/mol. Except for small molecule thermochemistry, we found the same trend as κDSDX-PBEP86-D3BJ for the remaining subsets. At small cX,HF, regularization seems slightly beneficial for the small molecule thermochemistry subsets (see Figure and Table in the Supporting Information).