Ubuntu support for 5K (Dell UP2715K): adjusting details

I've recently purchased a Dell UP2715K which has a resolution of 5120x2880 and have installed ubuntu 15.10 to go with it. The UP2715K is connected to a GeForce 960 GTX (2 displayport cables since 1 cable alone would not handle the bandwidth), and as such the display is actually seen as two 2560x2880 monitors, hardware-wise.

Ubuntu installs just fine, and after installing nvidia drivers the display ran at its native 5K resolution + HiDPI scaling works, and the image is just wonderful. However, ubuntu still seems to think there are two displays for a few purposes, and I still have two small issues:

• top menus don't go across the whole screen

• maximizing windows only leads to them occupying one side of the screen

Question is: How can I fix these issues? Is there any way the OS will really only see one big 5120x2880 screen?... I tried poking around with display settings + nvidia configs but didn't manage so far...

Edit: Unfortunately the maximization issue also means I cannot view content such as netflix in true fullscreen... which is rather frustrating. No success so far, tried several distros too (Kubuntu, Mint, ...)

The driver does see the monitor as one screen but it also tells the window manager that there are two independent panels, which the window manager then uses when maximizing windows.

You can enable the Video Wall script in KDE to make it use the whole monitor under some circumstances, like for video players, without using Xinerama. See the answer here.