I use 3 U-bolts for my grates- slightly more support than 3 regular bolts, I guess. I use U-bolts because they are round, so I don't scrape myself reaching down to the fire basket, and I also use them to mount my fire basket when in the upper grilling position. I have 3 legs sticking out from the basket that rest on the lower set of U-bolts, and they each have a stud sticking down to fit into the U-bolt so it can't slide off. I use SS acorn nuts on the outside of the drum on the U-bolts for nice bling.
I just measured mine, and there is about 5" of grill outside of the straight line between U-bolts. It would be hard to get something heavy enough to tip the grill in that small space. It's never been an issue.
I'm very intelligent, but I mask it by doing stupid stuff.