[phenixbb] Changing NCS groups

Hello, I would like to edit the NCS information for a model with two chains. I've tried running find_ncs and editing the phil file, but I get an error when I try to use my edited file in the next cycle of refinement. I've tried using the utility to detect NCS groups, then edited in the little windows - also no success. How are other people defining NCS when they aren't content with the equivalences the program finds? Thank you for your insight, Marie