Bed Use with 5th Wheel Trailer???

We have a short box and it creates some limitations. I have learned the hard way to either tie stuff in place or make sure it sits lower than the hitch. Two years ago the hitch munched an aluminum ladder that fell against it when going around a corner. Last month the hitch got hungry again and ate a cooler that slipped too far forward. In either case the hitch and kingpin assy went undamaged but destroyed whatever was in its path. I am resigned to either putting stuff in the trailer or lashing it down to the bed.