A week before the Fremont hike, I grabbed a Shimoda Designs Explore 40 kit from Glazer's Camera. After transferring my gear from the LowePro to the Shimoda, I weighed it and it came out to only 24 lbs. Once I fully loaded the pack with extra clothes, food, water and the extra photography gear needed, it topped 42 lbs. Despite the extra weight, and with a pair of hiking poles, I made it up and down the mountain with my back in far better condition than the previous 2 weekends.
If you read my review, you'll know I really like my Lowepro Freeline 350 BP backpack. Despite all of it's improvements over the Peak Design backpack, there's one outstanding regression in the design and that's the shelving and dividers. Peak Design's origami inspired shelving system is possibly the best solution I've seen for carving up bag space to organize and protect your camera gear. Lowepro's solution is adequate but inferior. So I decided to combine the best of each into a FrankenBag.
About a month ago, LowePro began to ship their newly design Freeline 350 Backpack. The one thing about the Peak Design pack was the fully configurable interior using a unique shelf design instead of a series of hook and loop pads. LowePro borrowed this interior design, improving it by making the whole system removable, not only to give the backpack more versatility but to make configuring it far easier. This was the first thing I noticed.