I have a space case fitted on top of the front box of my hardfloor, I use it to carry 4 camping chairs levelling ramp, high lift jack base plate (used to go under the jockey wheel to stop it sinking in sand etc), and a small ladder. The space case is held in place with a chain each corner from the handles did an to a tie down rail each side of the front box and turnbuckles to tighten the chain. I had a friend use ratchet straps to secure his space see in the same location, and he ended up with cracked welds in the corner of his front box, I reckon the straps were stretching allowing movement up and down of his space case which caused the cracks.