I'm using this code to detect the user's Documents dir: https://stackoverflow.com/questions/6227590/finding-the-users-my-documents-path/...
But it seems like that doesn't properly detect when the user has a non-default Documents dir location? That's frustrating, sorry. It looks like there's a module (called winshell) I could use to detect this. I'll add that to my TODO list.
In the meantime, if you're running Win7 or later and don't mind a bit of command line fiddling you could make a symbolic link between your default Documents dir's Playscii/ subdir and your desired Documents dir. https://technet.microsoft.com/en-us/library/cc753194(WS.10).aspx