I randomly jam my sleeping bag into its stuff sack. I pack it low in my pack, at the bottom. That locates it just above my hips. I think the rule, as I learned it, was heavy stuff near one's back, which seems slightly higher to me than the bottom of my pack. Back when I packed with an external framed Kelty-clone, the sleeping bag was strapped on at the bottom, too.

My food tends to go in near the top, but my clothes sack seems heavier to me than the food. Luckily, the entire pack is now much lighter than when I began backpacking, so the old rules seem less important now, too.