I preferred not to overthink the problem. I raised the sound.
My old Von Schweikert VR2 speakers had a rear facing ambience tweeter. The soundstage height seemed stuck at speaker height so I cut up an index card, glued it between two 1/8" pieces of MDF, painted it black and used double sided carpet tape to attach it below the tweeter. Voila! Soundstage height along with a cavernous space up to the ceiling behind the speakers.*
Ambience Enhancer
*User results may vary