In which case I am all outta ideas
I see you have posted over at Hyperpin. Undoubtedly they will advise some of the same things I advised and then its play with different driver versions I guess. When you fix it let us know the fix. If I ever have the cash to build one of these things I will need all the online help I can find
Although please do try with monitors 1/2/3 all in a row like little ducks.
So I finally worked this out, and it is kinda annoying/disturbing to find the answer. The Hyperpin backglass works on the second screen ONLY if the third screen is not 'touching' the primary monitor, otherwise it jumps to the third screen. The reason non of them were initially working was my UVP server wasn't installed properly.
So to get around this I have the secondary monitor set to 1366x720 custom res and then the third monitor set to 1280x720 and I float it on the horizontal so it is centered underneath the 2nd monitor. This way the third monitor doesn't touch the primary monitor, very crazy and I'm concerned that the third monitor may be 'snapping' back to touch the primary on reboot.

Anyway, at least I'm starting to understand the nature of this very quirky set up, if it continues to give me headaches I may have to drop Future Pinball as that's the program that's forcing me to have my third monitor under my second one, unless of course I can find a way to get a DMD from FP over to the third monitor as an individual element rather than some weird extension of the second monitor..
PHEw.....too many monitors.
