A whole inch extra. I wish I had that much. I decided I really need to have my camper aligned within about a half inch or less. The tight fit is at the very back so it is always deceptive until I backup almost all the way and then find I am not aligned.
I finally solved the issue with a $40 laser level from Lowes. The level has a massive magnet which I attach on the wheel well. I calculated exactly where to point the laser and I back up slowly for a perfect alignment. At least that is what happened on my first try. This year will be my second try with the laser so we will see.