Is the receiver just bolted to the bumper tube or is it welded to the frame of the trailer makes a big difference.
If you measure from the rear bumper to the center between the tires
then from there to perpendicular with the ball you can get a basic idea of the percentage of length behind and in front of the axles. eg if axle
was dead center 5# added to bumper will remove 5# of tongue weight like a teeter totter, with tandem axles the effect may be even less.
It is recommended to have 10-15% of trailer weight on the ball to minimize sway, less than that can contribute to sway, not something you want to experience.