This set up takes a lot of patience and can be physically and mentally exhausting. When I set up the left speaker I focus on the quality and impact of the bass but also how clean, clear and smooth Jennifers voice is. You have to go slow and after you find a few good spots you need to move the speaker a millimeter at a time till it sounds best.
The right speaker may not necessarily end up the same distance from the walls as the left. You center the image but you also have to pay attention to the bass clarity and smoothness of the vocals. It will then come together but I have not been able to get the center image to float in the center as well as I would like but may be a limitation of the Klipsch Forte speakers I am using.
I have been shoving speakers around many sound rooms for decades, used the rule of thirds, fifths, sevenths, and used the Cardas set-up. This Sumiko method seems to make the speakers sound their best but you need to have a lot of patience and a forgiving household.