I knew a fellow who drove into an approach (drunk), the sudden stop projected a refrigeration compressor through the cab, removed his head. I shudder every time I see people carrying firewood, or frozen sand bags in the back of their trucks for winter weight. I came up with a better solution.
I made up blocks of steel plate, through drilled, underslung on both sides of the tow hich. Perfect weight distribution, leaves box unobstructed and free of deadly projectiles. If the weight ever did come loose in an impact it would shoot under the truck. Mounting and removal is easy with a trolley jack.
The truck is up on my land, I will have to search for a pic, or take one once up there.