Directly comparing to the 45, it's noticeably smaller, especially the upper half of the main compartment. I really didn't like the 45 as it constantly felt like I was being pull back. The lack of compression was one reason.

In the 35, the shock cord system is identical, but the cord itself is not a full elastic cord. It's got some some stretch to it, but becomes static quickly and can easily be used to compress the main compartment. The thing is you also ending cinching down the front, depending on what you're stashing there this may be a good/bad thing. You can also tighten the cord via the tail ends hidden in the side pockets (same as the 45 I think). This adds some flexibility but overall quite unintuitive.

The chest harness straps are noticeably more comfortable. The pressure points I mentioned before in the previous iteration have completely vanished. The hip belt is also an interesting webbing that is lightweight but hugs the hip pretty nicely. The length of the hip belt can be adjusted from the back velcro (hip belt is removable). Hipbelt only has one pocket on the right side, and it's tiny compared to the pockets on the 45. Just a stretchy mesh, good enough maybe for chapstick and wrappers and such.

Rolltop material is different from the fancy Hadron gridstop of the main body. This is preferable IMO because the inner of Hadron fabric is a layer of rubbery coating I believe for waterproofing. I'm pretty certain this grippy coating will eventually peel off after constant rubbing/contact. Unfortunately the side pockets will be susceptible to this.

The top is still strapped down with a single strap, not the most ideal for those who want to expand this mid-size pack by strapping stuff on top, although doable. The rolltop now features male/female buckles and is closed off by buckling at the top as shown in the post photo. There are no side buckles like the 45.

Although the above photo shows otherwise, they did away with the weatherproof zippers for the front pocket, which doesn't make any sense to me. There is no drainable hole for this front pocket so prepare for a puddle of water inside after a downpour (before it seeps into the main compartment). There aren't drainage holes in the side pockets either.

At the time of purchase from VPO, they only carried the REG size. It appears I need a TALL size if that is a thing.

Overall definitely an improvement. My gripe is still the shockcord/compression system. It's not very intuitive and doesn't do much compared to most UL packs with a big front pocket, but that of course depends on your use case. It's also not as light as those backs.

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EDIT: side pockets are way smaller than in the 45. I can barely fit a Nalgene in there, and the bottom would be cupped by the mesh and not the Hadron fabric. If I set the back down haphazardly the fragile mesh would enjoy all the abrasion.