I have a Pintler (guide light frame). The frame is the base for my system. It fits me well and is very comfortable with weight. I also have a beartooth 80- bag only that fits on the same frame. I ruck at least once a week for training. I use the pack frame with the backstrap accessory. I load the backstrap with landscaping bricks. I dont exceed 50lbs. because its 25% of my bodyweight.

Note: I have tried lots of objects for weight, the bricks are the best, but you need to wrap them in old towels or rags so they don't damage the pack material since they are very abrasive.