Dipole rear speakers ???

My first thought on your seating possition (2' from back) and monopoles mounted on that same back wall, is that you're compounding your "boomy", "peaky", "low fidelity" bass problems!!! This won't sound very good. Infact, you can forget any audiophile refined applications here, or even good "midfi" sound from this setup! You and your speakers are then located in the most bass heavy/peaky spot in the room!...not the way to do it.
I would go for dipoles on that back wall if you must, because they'd likely be much better balanced to be on the back wall vs. monopoles(which more often than not are better balanced out in the room more!) (if you doubt, just measure and find out with test tones/sound meter).
Also, dipoles are more diffuse sounding mostly, which lends to a much less specific and distracting experience back there. You get lost in the movie much better, and they're less intrussive.
If you gotta go monopoles, they're trickier to make dissapear if you ask me.
Good luck

The cancellation issue mentioned by mrrobbcc above does not really exist/come into play from my experiences. You do however want them above your head somewhat ideally. For what you are doing I still like this setup.
Actually, mounted on the ceiling (how high again?) is the better option.
Dipoles are diffuse enough to still be more "non-specific" if you get em up higher. Sure, you ideally want to sit in the null in relation to where the drivers are, but there are compromises. And I still think placing monopoles back there will be a worse choice from an overall sound perspective, in that the sound is booomy and colored, which is the antithesis of proper sound.
The only alternative there is really "Equalization" likely, which is what I'd do, if I didn't do extensive resonators on the wall or whatever. Good luck

Also, you could easily mount your dipoles upside-down,firing toward the floor and ceiling along sides and on the back wall, if need be. Still a better option likely than dirrect firing on the back wall in your sitch, without any other considerations