No performance improvement was observed for LASSI [3,q] series. LASSI [2,10] wave function still has another 30 times fewer model states than the 52920 single determinants in the CASCI limit. All corresponding absolute energies are in SI table II and III. For comparison, CASSCF predicts a J coupling of -7.3 cm -1 , as opposed to the LAS-CASCI limit of -3.8 cm -1 , which suggests that any inaccuracy in the LASSI [1,5] result is more likely attributable to the LASSCF orbitals than to the LASSI approximation.