Whatever you are backing up, why not get a step ladder and simply set it up directly behind your vehicle, actually touching the bumper. Then simply sit in the seat and turn your heard and also check your mirrors. OK. Sit there for 5 minutes and just study that image in your mind.
Next time you back up (live), you'll have that image implanted in your mind and you'll know exactly where the back of your vehicle is. This works for a hitch and a travel trailer too. And this is something you can do right in your garage if you want to. It works. I do this with every new vehicle I get. 15 minutes well spent will save a life time of frustration and guessing.
Yea, back-up cameras really are great! But nothing beats your own experience.