You really just have to go into a parking lot to test you limits, both backing and forward so you can have a feel or it. Turn as tight as you can forward in a circle to see if it would even get close. It may not. As you doing that, think about dips pulling out of a parking lot, because the nose can hit the cab in a dip even if it wouldn't have level. By experimenting, you may learn you would only ever need it if you were backing into a tight spot.
You'll get a feel for what kind of turn you can make before you need to worry. Our last rig with a SB Ford and short pin box by 5th Airborne kept me too close for comfort most of the time, so I used the slider when I pulled into a campground or storage, when I had to pull into a tight gas station or parking lot. Not a great convenience. I eventually went to an electric release on the Reese slider, but I don't think they make it anymore.
