Let’s address the elephant in the room — what are your room dimensions and on what wall are your speakers situated? Not sure why this critical info has to be a national secret. Sheesh.
Probably because everyone will tell me to give up & quit bother trying?
Okay, from the bare wall I am using to place the speakers along to the integrated book cases(s) that cover the back wall is 8'4. To the left of that is a even boundary, that I have been referring to as a wall for the purposes of measuring, is a gun safe and a file cabinet, they are about 5' high, and they double as an equipment stand for my amp & CDP; above them & attached to the real wall are two shelves which hold my preamp and the power supply for the preamp and several pieces of gear that are being unused at the present--therefore there is no gear behind or between my speakers. From that boundary to the righthand boundary is about 8'. This boundary is a file cabinet and book cases filled with books and CDs which extend up to a shelf near the ceiling also filled with books.
Using the formula @bigtwin provided I started with slightly less than 27" from 'front baffle' to wall and 22.25" from center of tweeter to side boundary. These are B&W 805s. I tweaked them to 27" & 22". Without getting up & measuring, I believe center of tweeter to center of tweeter is 47" and to achieve a ear equilateral triangle, I have about 21" behind my ears to the book case laden rear wall.
As I have previously typed, in the past I had height and a lateral sound stage that extended beyond it's boundaries. There was/is a less clearly defined sound stage from front plane to rear wall, but none the less, a sound stage. I lived with what I had before, trying occasional placement tweaks, but it was a couple of recent threads here & in amps/preamps that got me going on this recent endeavor to see if I could achieve more in this small flawed space. However, with the lights off & my eyes closed, my speakers to disappear.