Like NightHiker, I have my heavy gear down low, near the hip belt. In fact, my layout is very similar to his.

water, flashlight, knife, FAK in outside pockets. rain gear on the top in the main pouch. Food usually under that, so it won't crush (some snacks easily accessible). Sleeping bag usually on the bottom, more cuz it's bulky than heavy (this is in a camping pack, not BOB).