I feel your pain. I had to do the same with the back speakers. They are as low as they can be, which isn't great for my back row, but works just fine for the front. Those channels don't get used all that much in my experience.
I think a lot of folks on here would benefit from a 5.1.4 config over 7.1.2 or even 7.1.4 like I have just because the back channels don't get used much. I'd rather have more in the front or ceiling if it helped with overhead effects.
If I were to do my room again it'd be larger footprint as well as taller ceilings.
@AcuDefTechGuy went with 12' I think and that'd be excellent. Lot of config options with that sort of room. Check out his theater thread if you haven't.