Incidentally, anyone who's hiked will tell you that the best position for heavy weight is at the very top of the pack. The reason is that this puts most of the weight on your hips rather than your back.
Women seem to prefer weight lower in the pack than men, even if equal height, because of a generally lower center of gravity. I nearly broke my nose carrying a male friend's pack briefly while hiking -- tripped on a tree root and was so unused to the high center of gravity that I smashed my face into the ground. My own pack was heavier (yay food!) but sized and packed very differently.
No, the bottom of the pack is completely outside (behind) the hips. If you put it at the top of the pack, you'll naturally bend forward slightly to an equilibrium between your torso and your backpack, the top of the pack will be roughly above the hips.