Front rack, certainly. Uprights are awful on hills with that much weight on the back.
Emergency P-clip(s) in the tool kit, along with the spare M5 and cleat bolts?
To date, the only failure I've suffered was a bolt working its way loose (suspect I'd partially stripped the threads, and off-roading with a camping load finished the remainder off) and vanishing. I botched it in the field with a cable-tie, and replaced it with a longer bolt and nut (it was, thankfully, non-drive side) when I got home.
If the rack's properly secured at the top, it doesn't actually wobble about that badly with one bolt missing.