Set position of secondary screen Mac n00b here. I'm running an iMac (OS X 10.10.4) with a projector attached as secondary display (extended desktop) and I have to set the position of this secondary screen in a way that the two screens align exactly at the center. My primary screen is of resolution 5120x2880, my secondary of 1920x1200, so I would have to place the latter at exactly 5120/840. 

Doing this using the GUI in Displays -> Alignment seems to be next to impossible, since there is no snapping at the center. Now I'm thinking, is it possible to to this via scripting somehow? Or by editing some screen setup config files?

Thanks much!
osx-display-positioner is a command line tool which lets you save and restore the position of multiple displays. The description of the tool doesn't discuss using it to set the display position, but if the settings file is readable and editable, you might be able to use it to accomplish your goal.