The "keepers" are not a necessary item. They are used, as you know, to keep the spring leafs aligned. However, if the u-bolts are properly torqued the springs will not and/or cannot move far enough to touch the tires. After all they are, like you said, just light tin straps which would not take much force to break or stretch.
Brenda, Karl and Lucy the spoiled cat.
2008 Dodge 3500 drw 2wd
2012 Excel Wild Cargo 41GKE