Weight on bars.
I ran this setup a few years ago with everything on a Meca System bracket attached to the triple clamps. The weight was never a problem even on 500km days! Even with the organisers GPS which was at least a couple of kgs it's self. A previous poster mentioned that the weight is quite far back (as opposed to frame mounting) and I think this is maybe why this setup works.
"What could possibly go wrong"
CBVRacing. "The race (Dakar) is what it is, it is being offered to racers, if they chose to sign up they should know that there are only 5 outcomes at the end of the two weeks: Finish, Mechanical, Abandon, Injuries, Death."