I have the same bag, been using it around 2 years on and off, only bag I've used. I don't ride with that much in it most the time, but i've gone with 40lbs of loose power tools, a few times with a 50lb computer in it 3 miles across town, and recently a grocery trip that filled the bag to it's max, straps all the way out, 68 lbs (i weighed it at home just to see how heavy it was), 4 mile ride home, and other than a pretty sore shoulder i had no problems. There was very little movement in the bag. The strap always works just fine for me as long as it's adjusted