Looks good, although it has compromises.
I'd move the fronts away from the corners (at least 0.5m from sides and wall).
And I'd also move the sofa a bit into the room, centering it also (once you avoid the chopped piece of the room because you moved the sofa in). Move it so that you make an equilateral triangle as commented before.
Look for a soundstage as wide as possible, but not so wide that the sound from right and left tear apart from each other. Voices mixed to sound in the middle are also a good reference. They must appear solid in the middle. Toe in and look for depth. More toe in makes more depth of soundstage, so that you get more layers of sound, each of them further apart. But if you go too far, the sound will collapse quite a lot in the middle, and instead of these layers panning from side to side, you'll have all centered sounds very deep, and sounds on the left or on the right located directly at the speaker position.
Then the rear into the other corner of the chopped piece of the room, and the other rear symmetrically. I guess you'd get a better soundfield then. I'll make a drawing if I have some time.
You can also do it and just test how it sounds (leave it at least for a couple of weeks!). Then, go back to "normal" and see if you are missing something.
If you leave it as it is now, check how it sounds when you block the rear ports (if present) with socks. Rear ports will resonate if too close to the wall, and stuffing them should alleviate this (although it also sacrifices some bass extension, which won't matter if you have a subwoofer).
BTW, the pdf is a nice and interesting read.
Badger, I don't see any physical/acoustical reason why the speakers should be exactly 4m apart. But I am "only" 29, after all
Maybe I am missing something (I doubt it
. Just joking
).