I've been working with the input port code in mame a lot lately and I'm not sure Mame on Windows could handle 2 spinners. There is an OS specific map that maps mame inputs to OS inputs. In the code_map, a second dial is an ANALOG_VALUE_INVALID. If you think about it, what are you going to map the second spinner to? You can have more than one mouse in windows but the all control the same pointer. You might be able to map one to the mouse x axis and the other to the mouse y axis but I'm not sure how.