In process on the Poser 12 installation.  It should be noted that the installation text file still refers to moving the contents of  the  'Custom shaders' folder into the Custom Engines folder; I think it is actually referring to the 'Engines' folder in the zip file.

To my pleased surprise, 3.1 DOES run from Scripts Menu in P12.  No idea what I did wrong the first time.  Did the same things: imported the definitions and presets.  I'm now going to delete the .pyc file and install the updated files from the latest P12 update and see how that goes.