Thanks for the idea. I think I know where I want to go with this for now, but until I start to build it out and see if it's going to work well it's hard to say.
Been fighting some monitor issues these past few days, typical buggy Nvidia crap with monitors not reporting properly and other niggling annoyances. Making progress though, I have the back glass at 1280 x 720, ultra wide at custom 1280 x 480 and play field at 1920 x 1080. The projectors will be set up as one monitor and I'll just split the signal to both of them, that monitor (#4) will be set to mirror either the back glass or ultra wide for now. Later on I'll see about making it it's own extended desktop and play with sending unique art to it.
Having a weird issue with HyperPin where the back glass won't go to the secondary monitor, it sits under the main play field on the main monitor. I have the settings set to display the back glass on the secondary monitor in the settings.ini but for some reason it doesn't want to go there.
Maybe it's a Run as Administrator issue as I'm using Windows 7