I (personally) would have thought that a towball would be a reasonable attachment point, only because of the way they are built as suitable to tow a caravan or camper trailer etc, and handle the breaking and accelerating encountered in touring.
When you watch some of the video's of you guys going up to Cape York, the force on the towball, as you go down into the creeks and back up the other side would have to put excessive force on the towball.
I'm
NOT suggesting a towball is suitable for towing, I just watch in bewilderment at the force that must be applied to it when used to transverse some of the gullies and irregular creek and river crossing seen on your video's.
Maybe 'lady luck' has to form some part of the equation