Thanks mitu - I didn't know about the es_input.cfg file. That's what I was looking for. My inputs don't overlap between the two boards, so I thought I'd be able to edit that file manually and create something that allowed for more than one player to control ES UI, but I couldn't get it to work. Not a big deal - player one controls the ES UI. As far as I can tell, using four players across all the boards works in the retroarch.cfg files for each platform and that's what really matters. Thanks for your help.
