I have the same rack and also used bolts, rubber and metal washers and nylock nut to secure the adaptor. I found the nylock nut to loosen one or 2 threads over time (then stop) so the rubber washers act as a damper. As for failure, I have read of a couple and seen one "online with pictures". Users claim rack was not overloaded. Anyway, on my last trip into Mexico, the SW Motech rear rack with 38L top box held up fine. On a previous trip, I had a Metalmule rear rack with top box that snapped and required re-welding. I keep my topbox pretty much empty when riding long distances except for a bottle of water (1L), some snacks and gloves. I only overload the top box when going from grocery store to campsite/accommodation (less than 10 miles). Anyway, since you have what looks like the 52L Givi, be cautious. The positive is South of the border, finding someone to re-weld is cheap and easy. Also, "toll" highways have no speedbumps. The "free" highway is littered with them.