for an extra couple of minutes, and an extra few cents, slugs with through holes could have been included that would allow one to tighten those bolts as they should be tightened. there also appears to be ample room to drill one hole oversize and insert those slugs into the rails from either side. that would make a sizeable improvement in structural strength in my opinion, since this is a "bolt on" setup compared to a "weld in" deal.