Although heavy-aug-cc-pVDZ (or haDZ) is computationally affordable it may fall short of the gold standard reference level of theory often used in the community. It is ex-13 pected that the delta correction error with haDZ would fall somewhere in between 0.1 and 0.25 kcal/mol, the errors observed with aug-cc-pVDZ and cc-pVDZ on either end of the range. To assess how good our choice of reference theory level is we have performed energy calculations with the gold standard reference theory level for a subset of 7 molecules from the benchmark set at CCSD(T)/CBS, where for the extrapolation to CBS the correlation basis is aug-cc-pV[TQ]Z, and delta basis is aug-cc-pVTZ. The gold standard energy is calculated as, 60