Question / Help Display Capture - Second gfx card / monitor 5+

[mtg101]

I'm running two graphics cards (Nvidia 1080s, not SLI'd) to let me have 8 monitors. When I set up a Display Capture, only monitors 1-4 (first gfx card) are listed. Fullscreen Projector shows all 8 monitors, so OBS can see them. I just can't set up monitors 5-8 to be display sources... Any ideas?