Capture Single Screen Mac alternative ?

Hi, I have been developing Unity applications for big screen shows (Magic, Concert ... ) with my company, and I am currently confronted to a most annoying problem. It is a problem often spoken of, yet I haven't found any solution for my particular needs. Here is the current situation : - I have a Mac Pro, connected to several displays (one or more). - I want the Unity application to play on one of them in fullscreen - I need to modify xml files manually on the other screen.

Having written scripts to modify game window I can do this while playing my application in the editor. But it's in the editor. I want to do it with a mac application. And I can't because the capture single screen is no longer supported. I get a Black screen whatever I do.