It looks like you are discovering one of the most annoying "secrets" about audio. It can literally take years to discover the ideal placement of speakers. Results are quite unpredictable, and shockingly small movement can have BIG sonic consequences.
When using the "Sumiko Method," sometimes moving the speaker an inch in one direction will significantly alter the bass balance of the speaker. This is both frustrating and positive (gives one hope of finding a really good location).
just keep plugging away.