Precise placement of speakers down to 1/4” only works if your own ears are totally symmetrical. Most of us have ears and eyes where one side is slightly favored by your brain and that’s why you have the balance control. Also, I have compared two CD players in my system where the same CD is presented slightly differently by each as far as imaging goes which I did not expect. Experimentation is your friend.
Speakers "Disappearing"
I have read a lot about speakers "disappearing" so that one can't tell from where the sound is emanating. But, what about all the stereo tunes where the recordiing engineer intentionally pans the music to come from one side or the other? Can the speakers be made to "disappear" in that situation? Or, is it just the nature of the particular recording?