[asid61]

Going off the load ratings for the 6800 bearings (10x19x5), which have smaller balls (like the larger inner race hex bearings) I would estimate them to have at the very minimum 200lbs static load or 400lbs dynamic load, which should be more than suitable for FRC considering that climbing is at its highest force during the climb/dynamic rate and that you're using two bearings. Plus, those ratings are for 1 million cycles, which I doubt any climber will see.
That doesn't take into account the stress concentrations on the hex, but it also doesn't account for the increased width or anything.