I woke up and read this post and did some testing and yes I have both buttons working. I'm using MAME 174 though it was easy to setup it seems that as long as you have the bios files you can just add the platform under MAME using the same command line that Brad illustrated. Then add a directory path to your games in MAMEUI and launch I found a few things tricky as for Beamrider you have to start the game by using number keys for options and by default button 1 is set to do two functions and at first does neither. I mapped the number keys to my d-pad, R analog stick, shoulder buttons and triggers then I could start the game. I tested with this game specifically because I know it uses two separate buttons.