I was able to make a relatively lightweight pack frame from the lengthened ALICE pack by making my own straps from some lighter commercial straps. It's important to understand how the MOLLE straps adjust, even if you don't use them. The original ALICE straps are not a good choice, because they don't use load lifters or allow for any real adjustment. The MOLLE pack frame and straps do. The MOLLE pack frame uses load lifters and allows for longer frame systems. The MOLLE system is good, but heavy. I borrowed from them to create my own adaptation. If you are in England, you may not have access to the components that I used, but you probably have access to something similar. Even though I sew my own straps and bags, I often start with a commercial product and a seam ripper to create something more to my liking. Oftentimes, the only thing necessary is to strip off the parts that you don't need. Since we are talking about external frame packs, I would look to the military packs and frames for ideas. By combining two frames, I was able to create a new frame with a longer length that I could set to my liking.