I did the Amageza with a exstra 8.5L on the back with tools etc, and my sub-frame mounting bolt (left side) broke off. I only discoverred it on the sunday (2nd day) with about 50km left to the finish. After I thougt about it, it allready broke to Saterday on the special stage, because the bike was moving around as soon as I went into n corner, and thought it was the extra weight, until I discoverred this.
Keep the bike as light as possible at the back. I will not put more than 5 kg's at the back again. Also replace the bolts if you think of doing this.
hope it helps.