Hi, I took a punt and bought a J5 USB to VGA connector to add another LG 27" monitor. I have previously setup a Thunderbolt to VGA adapter which is working well. Result is brilliant. I have read through the various forums etc and the Apple Genius Bar said no way two external monitors would work, even with a mid-2012 Macbook Air. I thought I should log in and let people know that is rubbish. I just ran video on both screens, there is no lag or loss of frame rate other people seem to had. The only issue, slight, was adjusting the screen resolution. Go to System Prefs and the second screen adjustment box on the second monitor allows you to fix that. Two monitors with the Macbook Air sitting in clamshell mode is pretty cool.