Created attachment 487589 [details]
screenshot showing the placement of 4 xterms started automatically at login

Description of problem:
I've this sh script which I've added to gnome-sessions services to start (back in gnome2 when there still was a UI for managing those), which starts 4 xterm's as part of the session startup.

gnome-shell does a reasonably ok job of placing these in a 2x2 pattern, except:

1) The bottom 2 are placed in a way which makes their title bar (but not the window contents) overlap the bottom of the top 2. Which makes it impossible to read the last line of the top terminal while looking at the bottom one.

2) The bottom 2 are sometimes not placed at the same height, see the attached screenshot.