After every restart, I have to manually set the resolution of my second monitor with:
sudo xrandr --newmode "1600x900_60.00" 118.25 1600 1696 1856 2112 900 903 908 934 -hsync +vsync
sudo xrandr --addmode VGA-0 "1600x900_60.00"
Unity never picks up the resolution automatically, so is there a way to set this permanently so I don't need to do it every time?