My 40L pack was too big for 3 years, a hostel guy in Lisbon fixed it
I used to cram everything into a 40L Osprey and thought I was smart for packing less. Then this guy at a Lisbon hostel saw me lifting it onto the bunk and said 'dude, your back is gonna hate you by day 5.' He showed me how he rolls clothes into 1L dry bags and hangs them off the outside straps, so the weight sits on my hips not my shoulders. I swapped to a 28L daypack with a 15L duffel for laundry and winter stuff, and now I carry 11kg instead of 17kg. Anyone else found that downsizing the main bag makes you ditch half the stuff you thought you needed?
Physics is the real fix here. Hanging stuff off the outside moves the center of gravity back, which actually makes the pack pull on your shoulders more, not less. Putting the heavy dry bags inside and close to your spine is what gets the weight down onto your hips, the outside stuff should just be light junk you barely notice.