Many thanks to all those who followed up with me both on and off the list. I notice now that 1LKS structure factors include hkl indices that violate reflection rules for A1 (general: k + l = 2n). The reflections in violation would have to be removed in order to reindex to the well-known primitive triclinic for lysozyme. Knowing this, reindexing is not a viable option, so the update will need to be P1 with ncs (either via explicit coordinates or matrix set).