I have a couple of ALICE pack frames that I extended for carrying heavy loads. For the first one, I cut two frames up and welded them back together to make a long frame. I used MOLLE straps and padding and added load lifters to the frame. The second time, I replaced the aluminum tubing with a thin stainless steel tube frame and top crossbar. I used straps and padding from a load carrying harness that I cut down to make lighter. Both of these frames were comfortable to me, if a bit heavy, but not too much. I could carry a fifty pound bag of dog food on these fairly well. I used these to pack glacial boulders out of a pond excavation and used them for landscaping. I packed several tons out.