Hi Chaz,
I know it might be late on this, I play using the 8BitDo SN30 controller. Try to see if your controller has an Input mode.
If there are different modes, on the back of the controller is a sticker with instructions on how to change the modes. Usually by pressing Start + X or Y or A etc.
I believe XInput makes the controller connect as if its an XBOX 360 controller. Experiment with the different modes until you find the one that works with PSO!
Hopefully that helps,
Sflores91