If you are running just a 5.1 set up do you recommend a set of BPs over the Bs?

Since I don't really have the option to wall mount on both sides the BPs are probably out and I dont have any room to place behind the seating area so can't really go 7.1 I figured I could get Bs for rear in the 5.1 now and then when I upgrade to 7.1 at next location get the BPs to fill in the side?