Given the success of our methodology in reproducing Diels-Alder results, we turn to the 908-reaction subset of RGD1 reactions for further testing. Our calculations show that this set of reactions shows a broad distribution of multiconfigurational character as measured by the M -diagnostic (Supporting Information), with 32% of reaction energies and 63% of activation energies demonstrating significant multiconfigurational character (M > 0.1), for a total of 68% overall. To account for the cases with the most multiconfigurational character, we have chosen large APC (12,12) active spaces for each state in these reactions. This active space size is significantly larger than necessary for most reactions in the dataset, resulting in inconsistent but unimportant orbitals between the reactants and products of some reactions.