Years ago a TBN member told of the "ride" he went on when his straps snapped and ths tractor rolled back at highway speeds. He managed to keep it between the ditches and in his thread he related what he felt happened. It's been a while so I don't recall the exact details, but even though he was well within the trailer specs, he figured it had flexed on a bump causing the straps to fail. He bought a heavier trailer and a good set of tires down chains as he didn't want to do it again.