Acoustic panels on ceiling

One more point just for future reference. Line sources or linear arrays the best of which extend from the floor to the ceiling do not send almost any energy to the floor or ceiling. If they are dipoles they don't send almost any energy to the sides either. The only reflections you have are to the front and rear walls and only the reflection off the front wall is early enough to matter. 

thyname, thanks for the link.

mijostyn thank you for the explanation.

I can see the obvious physical problem of holding and moving the mirrors while sitting in the listening position.  It does seem that having a ladder and friend (or wife/significant other), LOL, to hold the mirror would be pretty essential.  

The mirror technique will work if you can MacGyver a way to hold it and move it.  If it were me, I'd start approximately half way between ears and front plane of speakers, and then explore a little fore and aft.

The scientific way to do this is locate the sound pressure peaks greater than 6 dB above the average sound pressure in the room using a SPL meter and appropriate test tone. Otherwise, it’s like shooting blanks in the dark. It’s like trying to solve x simultaneous equations in x+n unknowns. 

…..you say you’ve been reading conflicting info. How are the answers on this thread any different from the rest?  Why wouldn't you be satisfied with whatever GIK tells you?  Just curious.