definitely a nice light pack the thruway,
i havent used frameless packs that size, seems to be a bit of an art to doing it and getting the pack to support the weight properly without sagging or digging into your back. backpacking light seem to be harsh judges in their reviews, they want everything just right... but its harder to do when you get a minimalist design that removes most of the support... thats the trade off, you get to save weight on the pack but have to be more careful in packing it and might have a pack that isnt as comfortable as a heavier pack, weight vs comfort....
the packs i use are the next step up. just a wire frame around the back and a plastic sheet for a bit of rigitity. but you can still over pack it and end up with a back that bulges out on the pack..