Marking your monitor comes in handy....
....if you haven't thought of this you might consider it.
I marked my monitor with very thin strips of colored sticky paper; yellow indicates the 3 foot line so I know when I am within 3 feet of the toad or anything I might be backing up to. The orange line is the at the limit of visibility 40 feet as I recall, (set this up almost a year ago. Strange that as close as traffic seems to get, it is rare that a car behind me gets within 40 feet.
An hour to fool around with cones or other things easy to see, a tape measure, and sticky tape in a bright color is all you need.
Gary, Cindy, Reacher (Maine Coon), and Vivian (in spirit only now).
Retired: July 31st, 2013 and loving it.
2011 Coachmen Encounter 37 TZ pulling a 2012 Wrangler Unlimited Sahara. Many upgrades, additions, mods, and changes.