Lorune, that is how mine used to be set up but I couldn't use PiP because of stretching so changed to

1 + 4 horizontally
Main: 1536x1200
2-5: 384x300
(will post a pic this evening).

This lets me PiP without losing aspect ratio. (the closest I could get with a widescreen aspect was

Main: 1440x900 (same as a 22")
1-5: 420x300 (you can actually have 7 of these

of course with 5 wows you will end up with a 420x900 empty region to one side of your main (put TS there maybe?)