There’s roughly 18" (i haven’t measured it) of movement on a slider, generally i’ve found the ideal position for correct weight distribution on the tractor is about the mid way point, which makes sense.
If you moved the slider from one extreme to the other you’ve in effect moved the trailer axles by the same amount, plus the pivot point on the tractor has moved.
All different trailer types maneuver differently just like tractor units, some tractors have a brilliant lock and fast steering some have less lock and require more turns of the steering wheel for the same effect, some trailers will have axles further forwward or back than others, any trailer with a lifting axle in operation will change things the most dramatically.
Its not just you we’re all the same, as Blue Estate has found doesn’t matter if you’ve been doing the job forever a different wagon or trailer type can leave you making a right pigs ear of the simplest of maneuvers.
You should see me attempt to reverse a container trl or triaxle curtain sider into a standard bay when i’ve been pulling tanks for months on end, looked like i passed me test yesterday 
One regular delivery point one of their fridge artic combos had been left in front of the silos, as i’m a regular there and none of their drivers in for several hours they asked me to move it and put it on a bay with trailer wheel guards, 6 shunts later and its somewhere thereabouts 