Speaker Positioning

Bosch laser measure, inexpensive model.  You can check the exact distance between you and the two speakers, and you don't need someone to hold the other end of the tape measure.

@twoleftears , +1 
A laser measure will be the most accurate.

@OP,
There are other measurements that can be considered. Sound pressure level, frequency response are just two.
If you are serious, why not contact a high end dealer to assess your system?
I bet you'll learn a few things just watching.
Bob

Start with a laser to (+1 on Bosch) to get each within an inch of each appropriate ear. Then fine tune (especially toe in) according to soundstage. If the wall placements are equal move one until it sounds best and match the other first. If not good luck.
Measurement and dynamic are oxymoronic.

check out the book “Get better Sound” or Wilson’s Audio Setup procedure in YouTube

I have a pair of speakers, this is the directions for speaker placement of the tweeter AFTER the toe is set. Take a laser pointer. Make sure it has a flat base. Take the flat base and put it on the face of the tweeter screen face (it's a ribbon). Set the tweeter at 6" or so over the head at the seated position, and tighten the adj screws..FST Free Swinging Tweeter.

Great idea, WORST place on the planet to mount it.. I'm fixing it.. :-)

The placement of every driver in every direction is EVERYTHING.

Man oh man is that hard...

Regards