I had a similar predicament in my last house with the couch on the rear wall and ended up mounting the rears quite high to maximize the distance to nearest seat. No one ever complained and given your expected compliment of speakers... could work well if surrounds are on the docket.Out of curiosity, why would this be an issue with 4.1 but not 5.1? I can’t imagine how the addition of a center channel would alleviate consistency issues with the rear surrounds at extreme seat positions.
In particular, what I want to remain possible in a music room setup is at least “good” sound even from a couch spanning the rear wall. It seems like the closer you are to the rear corners (if there are surrounds located there), the more distorted the soundstage will be due to the SPL of the surround increasing at 1/r^2 as r approaches 0 (as well as it’s time of flight decreasing), whereas with only wide beam front speakers there are no such “singularity artifacts” in the rear sound field to contend with.
My basement setup has F208's in stereo and a 2nd couch on the back wall. The sound back there is phenomenal. The wives don't complain.
I just skimmed the thread, so apologies if these thoughts aren't all that applicable.