When we had ours fitted the guy said that you should always have it behind the passenger side as then you have the seat back firmly against the seat and the stabilising bar firly agains the back of the back seat and it will not move = we had a 4wd hit the side of our car about a month a go and hit the passenger side and DD and the car set did not move an inch - you can push on the car seat and it will not move as the sabilising bar and the pass seat are holding it firly in place as well as the anchor.

Kate