We can extrapolate a little on what it's like to naturally apply force to something. The CR Report showed that it took 80 pounds of force to break 4 pencils. Those pencils don't really bend they just fail with a break.
The CR guy wasn't able to break 4 with his hands holding them similar to the YouTube guy. With 3 pencils it was fairly easy for him to apply enough force to break them. On a cursory analysis (far from perfect), we could say a quick and dirty assumption may be that each pencil takes 20 pounds of force, or 60 for 3 pencils. Since the iPhone Plus bends so easily doing the same action, it may take no more than 60 pounds of force to cause a permanent failure (bend).
More math is needed for accuracy as this is just extrapolation but may provide some reasonable estimate.
The CR guy wasn't able to break 4 with his hands holding them similar to the YouTube guy. With 3 pencils it was fairly easy for him to apply enough force to break them. On a cursory analysis (far from perfect), we could say a quick and dirty assumption may be that each pencil takes 20 pounds of force, or 60 for 3 pencils. Since the iPhone Plus bends so easily doing the same action, it may take no more than 60 pounds of force to cause a permanent failure (bend).
More math is needed for accuracy as this is just extrapolation but may provide some reasonable estimate.