My custom layout is:
ToonFirst,ToonMiddle,ToonLast;NAME
1,2,3,4,5,6,7,8;8/5;NAME;NR

You can configure how tall and wide your Grid Frames should be.
A full 40-man BG covers roughly a third, or maybe slightly more than that, of the horizontal space on my screen.

I use the in-game GUI key to bring up the console.
Then drag (re-size) my Repeater Region, to cover the entire raid.
Sync, Save, and close the GUI.