I'm staying for now on the 1.11u because of other compatibilities reasons.
I don't think 1.13 should cause you any compatibility issues - however 1.11u is pretty robust, so no problem staying with it.
Yesterday, I exported a material in a folder, then I moved the folder elsewhere. Just after, when I tried exporting another material, poser crashed just when I right clicked to export. It was probably because the pluggin did not find anymore the folder where it was supposed to export. Not a big problem, but there may be a little code to add in order for the pluggin to come back to the "initial pluggin folder" if the actual folder does not exist anymore. Note I think it is the reason, but I'm not 100% sure of it
Did you happen to get a copy of the python exception this raised?
Paul