How to place speakers at the optimum height

Your nose is on the same plane/level as your ears ... use your nose as a guide ... it's easier to see than your ears

DISCLOSER .. I am not telling you where to put your nose only to use it as a guide or reference point relative to tweeter

Make sure that the lasers are off when you are adjusting them while seated in the listening position.
I also think that as far as floor standers go they average about 3 to 5 feet. It is absolutely true the further you are from the speaker the vertical dispersion becomes less critical but using an 8 foot cardas triangle your head should be at the apex of the equilateral triangle so toe in is important. Remember it is your system and your preference so just adjust to your taste starting with those principles. Many speakers including my own have excellent lateral dispersion and don't require a lot of toe in. You will see, or hear, as the case may be.

Thanks for all of the response. I tried to raise the speakers a little higher and the result is that the singer seems to be singing from the stage, you know like from the concert and you are in the first row. Maybe I will try to sit way back in the room and see what happens. But isn't sitting way back would put you out of the optimum distance for stereo? When you place your speakers do you aim to have the singer right in front of you or sounds slightly above you?

I like 18-24" above the speaker. Not front row, more like 5th or 6th row. It gives the music a chance to bloom.

Not all speakers need to be toed in so much. As long as you keep a solid center, toe them out to get more sound stage width. If you hear your center losing focus you went to far. Most speakers sound there best a little of axis.