I got it to work, all i had to do was change '\\.\display2' from lower case to upper!

.
I would like to set this in Mame.ini as well as UME.ini so i dont have to type the prefix in all the time in the command line. I added to the mame.ini....
screen0 \\.\DISPLAY2.
But upon doing so mame kicks this out....
D:\MAME>mame ffight
SwitchRes: [ffight] (1) horizontal (384x224@59.63)->(1920x1200@59.63)
Unable to create the Direct3D device (8876086C)
Unable to initialize Direct3D.
000000000021E6F0: 0000000001718167 (not found)
000000000021EBC0: 00000000023718AE (not found)
000000000021ED20: 000000000171ED64 (not found)
000000000021EEE0: 000000000171CB42 (not found)
000000000021F100: 000000000171927A (not found)
000000000021F410: 0000000001E2FA3C (not found)
000000000021F600: 0000000001E30C5D (not found)
000000000022F3C0: 0000000001D57907 (not found)
000000000022F8A0: 0000000002067EBE (not found)
000000000022FE10: 000000000171B1E3 (not found)
000000000022FE60: 00000000023459EC (not found)
000000000022FF20: 00000000004013F0 (not found)
000000000022FF50: 00000000004014F8 (not found)
000000000022FF80: 0000000076BB652D (BaseThreadInitThunk+0x000d)
000000000022FFD0: 0000000076CEC521 (RtlUserThreadStart+0x0021)
Unable to complete window creation
D:\MAME>