All of the cargo boxes come with rounded u-bolts, with the rounded side down. That's fine, but I've never liked the bolts/nuts sticking up in my cargo box to scrape and poke holes in things. So I got thinking (as dangerous as that is for me) about a better way.
I'm thinking of taking square u-bolts, putting the square/flat end inside the box, threaded ends down. I'd take steel bar stock, cut pieces, and machine a half-round in the middle of them to match the profile of the rack tubes. Those would go under the rack, with a nyloc securing it. Or, maybe a steel flat pressed to half-round. Here's a quick-and-dirty mockup:
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Has anyone mounted a box like this? If so... how did it turn out?
Help me make this work, because I keep thinking of welding up my own rack, but I'm trying not to let those intrusive thoughts win.