Perfect Speaker Placement - Put next to the back wall as much as possible.

Hello,

I happen to find an good article about the ideal speaker placement. 
(Easiest version without numbers & formulas that I can’t honestly understand :D)

I’d like to share. 

Personally I find two things interesting.

1) Only use 40% of the room area (38% rule)

2) Put the speaker as close as possible to the back-wall (next to bass trap)

Of course, minor adjustment would be required depending on speakers.
Still, I think this is helpful to figure out the very first step. 

http://arqen.com/acoustics-101/room-setup-speaker-placement/

https://realtraps.com/art_room-setup.htm

Happy listening.

p.s. what should I do with half of the room left... :?