I have 2 U360s and they are great. However, I'm trying to put the keyboard away on this cab for good and just use the joy and buttons for everything.  I am using the U360 in input mode with the maximum of 8 buttons connected.  6 player buttons, a start button and a coin button for each player.  That means I'm going to need the "virtual" buttons working for ESC and possibly ENTER or a couple other functions.
Anyway,  how do I make mame see a different button for ESC?  If I try to do it in the setup, it recognizes the button 8 (the shift button) and then (virtual) button 9 as well.
TL;DR : What file do I edit in order to make mame see a button for ESC?  I've looked in mame.ini and esc is not there.  Looked in default.cfg and unless I need to enter an xml field manually (which is fine), i'm not seeing it there either.