I'm attempting to generate a symmetry file for a system comprised of two parallel beta sheets symmetrically related only by translation: the beta strands within the sheets are symmetric translations, and the sheets themselves are symmetric translations. I additionally want to keep the z-axis offset between the beta sheets constant, if possible, so I can change the x- and y- spacing between the beta sheets. I have had success with this in similar systems using the HELIX mode of the make_symmdef.pl program, but in this case there's no proper 2-fold axis, trying to use HELIX mode generates the wrong symmetric structure. NCS mode complains that the chains are only related by translation and won't do anything, CRYST mode is irrelevant, and PSEUDO mode defines a jump between the centers of masses of the sheets, which aren't lined up so there's a chance the z-axis offset will change. If I'm wrong about the PSEUDO behavior, then it should work fine for what I need. Otherwise, if anyone can give me any suggestions on how to set up these symmetry definitions, I would greatly appreciate it.