If you are looking to add some weight to your ruck without tearing up your pack or your back, check out the Padded Weight Pockets from Shaddox Tactical. They make three sizes for 20, 30, and 45 pound weights. These pouches are designed around GORUCK plates (or similar) to mount via PALS webbing inside GORUCK bags but they can also fit other bags.
These pouches are constructed from two layers of 1000D Cordura Nylon with closed cell foam padding between layers. The top flap is secured with Velcro and features a Velcro/PALS field for attaching small pouches or moral patches.
Check out the Padded Weight Pockets at ShaddoxTactical.com.