Alain, it almost sounds like you are overloading the poor bag. And your poor back. Try putting the heavier stuff higher, and pull it in tight. As I understand it, you are using a fairly large, frameless pack, basically in the class of a light camper's bag or a military three-day bag. That is how I load my packs of that class, and I snug them up high and tight to my back, and use the sternum strap, so I'm putting some of the weight on my chest, and thus my abs.

That said, if you feel the need, add the waist bag- more room for good stuff! <img src="/images/graemlins/smile.gif" alt="" />

I might also suggest talking to a doctor, or better, a chiropractor if the bag is causing you pain. He might have some pearls of learned wisdom to share about how YOU should load YOUR pack. After he gets done lecturing you.

I've been on the business end of that lecture before.