If you have no passengers in the back seat when you carry the dog, AND the dog will not jump over the seats, I find a complete cover on the back seat works fine. You can buy one that hangs from the front and back headrests completely filling the back seat area like a hammock, on this we put the dogs bed, a seat belt clip to the dogs harness and Bob is definitely your uncle!. They are available from any doggy type retailer for about 40 quid, or Lidl's, when available for £2.99, yes thats right, same thing! Or Tchibo when available for about £4.99 (they have been as much as £9.99. The great advantage is, when not in use, fold it up and stuff it in the back. I have used one on the A2 and the Volvo with complete success.