Surround speakers placement assistance needed

Hey guys. The back wall where my surrounds will go is about 20 ft. My problem is that the tv isn't centered, which results in my speakers not being centered as well. Of course, we rarely have perfect ht rooms to setup in. The right surround has perfect placement, being at the end of the wall/corner. The left surround is the problem, though. Should I place the left surround proportioned to the right surround, or can I place it at the other end of the wall? This would be about 3 ft farther away from center. Is it possible to just mount it at the other end of the wall and make level adjustments through the receiver?