Geforce cards do not allow you to set ID on the Outputs. The number of connected outputs are defined from Windows. Once you have reboot your PC, you struggle with putting correct output destinations to the correct projectors. After every reboot Windows will put your projector by random numbering.
MadMapper 4.0 will identify connected devices using the serial number given in the EDID. So it should solve this kind of output swapping issues. You can alwready try with the beta version (from beta 7 if I'm not wrong)
Also those problems donnot happen for me with my office setup (an nVidia 1080 with 4 outputs and an AMD with 3 outputs). Iread a few things about it. In some situations we can't solve, but MadMapper 4.0 using projector/screen serial number will solve (except if the manufacturer is not feeding serial number or setting the same on a whole production of the same device, but I suppose it won't happen with serious hardware as it even doesn't happen with my cheap monitors)
The stutter at 60fps was by far not so bad as it is with a P4000 with 4 outputs
We're working at making things smoother on Windows in 4.0. It should be out in the final release. The problem is synchronization between our engine => OpenGL driver => ... => projectors/screens is a mess on Windows, so we're investigating using Windows native things for the output. Should be in beta 8 if everything is ok. If you're interested to test, PM me.