Over the last couple years SUL has gotten increasingly poo-pood on this website from veteran hikers who would rather act manly and dirt bag. Fine, no problem. However, I don't think it ads much to the discussion.
I've been UL backpacking for a long time, and over the last couple of years, I've taken an interest in solo trips closer to my physical (and emotional!) limit which have driven me to reduce weight even further. I've gotten more fit, and more psyched than I've ever been to explore new terrain. One of the feelings that I live for in the mountains is to get up high and look at some beautiful far off feature in the landscape, and to feel totally empowered to just set off in that direction. No question, the lighter and the smaller my pack is, the more empowered and the more liberated I feel in the mountains. There is some incredibly beautiful and rugged terrain in my backyard, and its deeply satisfying to feel strong, fast, and at home, like I've somehow become a match for the landscape. Inevitably, I get humbled--I bail, I get lonely and I long for burritos back in town, but that feeling of liberated self sufficiency is a big reason why I do this.
No doubt, reading BPL articles on SUL in the early 2000's and seeing pics of RJ carrying what looked like a small daypack for serious multiday adventures opened my mind to a different, and I'd say, revolutionary way of experiencing the mountains. Thanks for reminding us, RJ, of that special SUL mindset.
I'm also in favor of scrapping the arbitrary 5 lbs base designation. I do think that staying in that ballpark matters as far as getting that liberated 'I could go anywhere in this pack' feeling. However, moving the definition away from a specific weight and toward a general attitude can help us to stop obsessing over oz's and spreadsheets, and spend more time training and scribbling on maps. Its not about the achievement of having that light of a pack, it about the new possibilities it opens up.