Merlin said

"Raising the to this height will give the correct spectral balance and reduce floor interaction. Raising them further will reduce floor interaction even further usually making them leaner than intended. It isn't rocket science."

My thoughts exactly .

James said

"Bass has become deeper, clearer and louder at phase 11, so they are less 'lean' than when they were lower down."

I wonder if this is due to the fact that your speakers are getting closer to the ceiling and are now being reinforced by the ceiling instead of the floor ?

edited to add ,

I seem to be a bit slow of the mark

note to self - must learn to type with more than one finger .