My solution on my 2011 +4 was to change the seats over. That way the worn bit is then on the inboard passenger side seat and not so noticable .
You will need to remount the seat belt fixed mounting on each seat (drill and bolt).
After you have done that ensure that upon entry to the car you step in carefully ensuring that your rear end doesnt catch the upholstery.
The only disadvantage is that the reclining levers can foul each other, although you could bend or shorten one of them, i havent bothered to.
