You can do alot with a little Each do-dad zipper, compartment adds weight. I finally ditched the trunk, and bought an REI 1lb "day pack" with one compartment with side pockets for wallet ect. Then inserting a plastic black school folder as a compartment (which also holds paperwork)

Total weight is usually 3lbs is avg. but sometimes up to 6lbs

Also fit is *really* important. There are several websites that detail how to fit a pack. The pack should not drift toward your shoulder joint. My pack has a chest strap to prevent shifting while underway.

Yes your back will be sore a little until you get used to the weight But after a week or so, it it's still sore, something's wrong.