My recommendation is to set up as a 5.x.x system, so Surround, not Rear.
Rears do get more programming now than they used to, but you can't really have a good sound field by eliminating the Surrounds.
Keep in mind, placement in most homes is never ideal, and we have to work with what we have; do what we can.
One other tip... since that back wall is so tight up on you, I would adjust the Elevations to either fire down at your position, or set them up as Front Height rather than Rear Height. Or, mount them to the sides and assign them as Top Front or Top Middle. I think this will give you a more believable Atmos effect and help create that Bubble Of Sound.
Cheers!