[Tammyo]

A disadvantage of a hook design may be that it would be hard to line up with a tote. Also, when you lift the tote with the hook the tote would not lift parallel to the robot, because you do not have enough points attached to the tote. This would result in unequal weight on your robot, risking your robot to tip.

I suggest you create a mechanism that is central to your robot's weight.