Regarding tight hip belts, I have envied some of my female hiking buddies with that "shelf" cweston mentions. A too-tight belt can be awfully uncomfortable. In my experience there are a few things you can do to avoid having to cinch the thing down too tight. First, avoid packs that brag about ventilating your back like the plague. You want that pack to snuggle against as much of your back as possible to add friction that helps keep it from sliding down. Second, avoid "slippery" shirts for the same reason. Knitted (stretchy) fabrics promote more downsliding than woven ones IME. Third, adjust the load lifters correctly. Fourth, lose that man paunch (that should really be #1).
I've found it to be just the opposite. I load my pack with the bulk of the weight in the bottom, wear the hip belt lower and as tight as possible. Moving the hip belt lower eliminates the pain of tightening by distributing the pressure across the bulk of the bone mass rather than pulling in the hips at the top. Then I cinch the top of the pack down just enough to keep it from sliding around. I know, all things that the old school backpackers would consider to be sacrilege. But I find that it takes the weight off of my back and shoulders. I can move much more freely, have better balance, and feel better at the end of the day.
4 out of 10,000,000 people surveyed do not like pie.