Ah lovely. An update that breaks things :(

Anyway, in the meantime I've found a much easier way to do Partial MAT files: Save an MC6 with only the materials you want to change, then change "mtlCollection" into "figure" and rename the lot to pz2.

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.