I personally never use any stereo imager or even any panning on the master. Instead i use built-in stereo delay plugin to get proper stereo width to proper elements. Just my own way 
BTW, anyone knows any professional stereo imager/enhancer plugin ? I have tried many but never find anything that sounds quite natural.
After trying several i find below two plugs best…
http://www.vengeance-sound.com/plugins-vms-sb-frame0.html
http://www.brainworx-music.de/en/plugins/bx_control_v2
Anyone else ?