I have a late 2013 13" rMBP and a 4k monitor (3840x2160) that's running at 60Hz over mini display port. Right now it uses a scaled 1920x1080 resolution so everything is displayed at 2x HDPI (retina mode), which seems to be default.
Everything is a bit big for my liking, however, and on the flip side 3840x2160 is far too small, so I was hoping to go for around 2560x1440 for a happy medium.
As System Preferences seemingly doesn't permit this, I downloaded SwitchResX, created a custom resolution ("scaled" mode and 2560x1440 resolution) and selected "save", rebooted, but it still won't show up in System Preferences.
What am I doing wrong? Is my computer not capable of displaying that resolution (I realize it has to scale it up to 5120x2880 first)?