Okay I guess I did get 2 controllers working at the same time!
I'm not exactly sure how I did it but here's what I think did it.
The red text are what I typed in the command prompt at the $ sign prompt.
The black blocks are the code inside the files that I edited with these changes.
If any of these nano commands won't let you save your changes, make sure to add sudo in front of them.
nano /opt/retropie/configs/all/autoconf.cfg
reicast_input = 0nano /opt/retropie/configs/dreamcast/mappings/controller_XboxGamepad\(userspacedriver\).cfg
[emulator] mapping_name = Xbox Gamepad (userspace driver) btn_escape = 316 [dreamcast] btn_a = 304 btn_b = 305 btn_c = btn_d = btn_x = 307 btn_y = 308 btn_z = btn_start = 315 btn_dpad1_left = btn_dpad1_right = btn_dpad1_up = btn_dpad1_down = btn_dpad2_left = btn_dpad2_right = btn_dpad2_up = btn_dpad2_down = axis_x = 0 axis_y = 1 axis_trigger_left = 10 axis_trigger_right = 9 [compat] btn_trigger_left = 312 btn_trigger_right = 313 axis_dpad1_x = 16 axis_dpad1_y = 17 axis_dpad2_x = 3 axis_dpad2_y = 4 axis_x_inverted = no axis_y_inverted = no axis_trigger_left_inverted = axis_trigger_right_inverted = axis_dpad1_y_inverted = no axis_dpad1_x_inverted = nonano /home/pi/.reicast/emu.cfg
[input] evdev_device_id_1 = 8 evdev_device_id_2 = 9 evdev_device_id_3 = -1 evdev_device_id_4 = -1 evdev_mapping_1 = /opt/retropie/configs/dreamcast/mappings/controller_XboxGamepad(userspacedriver).cfg evdev_mapping_2 = /opt/retropie/configs/dreamcast/mappings/controller_XboxGamepad(userspacedriver).cfg joystick_device_id = -1 [players] nb = 2Now I have 2 wireless Xbox 360 controllers working at the same time. I should note that I also have a USB keyboard and mouse plugged into my Pi so your evdev_device_id_1 & 2 numbers might be different than mine. Without those it might be 6 & 7 instead. To find out you just run evtest at the command prompt this should show you what numbers are actually needed.