I agree that a larger pack with heavy stuff in it will torque you more - the 80's and 90's proved that many time.

But I do take a larger pack than I absolutely need. (However,the Exos 58 I now use is 100 cubic inches smaller than the Vapor Trail it replaced, and is only about half the size of the Dana Terraplane I carried back in the day.) I could get by with a 50L pack, but everything gets compressed more than I like. Using a larger pack than is absolutely necessary, I find I have changed the way I pack. I purposely put my kitchen and food bags closer to my back and a bit lower, for that reason. Extra water (rarely more than 2 quarts) find me rearranging things so it goes next to my back, too. Clothes and my ultralight tent go farther away, and the sleeping bag doesn't get compressed as much, so it helps fill the bag. Previously, the kitchen and food rode higher and further away. I also find I use the compression straps more now to help shape the load. Before, everything went in and then the straps got tightened. Now, I'll tighten the straps a small amount, before anything goes in, to help put things in the pack where I want them. So far, it's working.