Sounds good.
I had a setup where I had to sit farther away than the equilateral triangle suggested due to room layout. It sounded very good and I was happy with it, but if I really wanted to get the best, I would take a cushion off of the sofa and sit on the coffee table which put me at the point of the triangle.
Honestly did not do that very often, but it let me know what I was sacrificing to the room layout. It wasn't enough to justify changing the room around, but enough that every now and again, when I played a favorite song and really wanted to fully listen to it, I would re-position myself!
But my main point is you might set up a temporary chair and see what difference it makes. I doubt the difference will be anything profound.