Personally, I try to put the heavier stuff (like my water bag and stuff) in the middle nearest my
back - this way it moves around less to "swing me around" as it does it if is on top or
near the outside of the pack and further from my centre of gravity - but try a few things
yourself and see how you are comfortable.

You shouldn't "hurt yourself" however you try it - unless you are already carrying a
really heavy load.