If nothing else is available, try for 41C or 41G. I happen to like these seats when 31 isn't available. They seem to have more legroom, they do have wider armrests and you don't get banged by the FA carts as much, they are 4 across instead of 5 across. It is a longer wait getting off the plane, but if it's a little more comfortable for the 12 hours your in the air then it's worth it. IMO

Good luck