You can save the materials as either a Material Set (MT5) or Material Collection (MC6)
in the higher version, then turn those files into MAT-pose (PZ2) by simply changing
a couple of lines at the top of the file.

Change the version number to 4 so the user won't get a warning message;

then find 

actor $CURRENT
 
in the MT5 or 

mtlCollection
 
in the MC6, and change either of those lines to

figure

Then save as a PZ2, and put it in a MAT-pose folder.

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