I have a size Medium. From the bottom of the hipbelt to the load lifter attachment points, it is 21”-21.25”. The top of the shoulder strap attachment point is sewn at about 18”, but the shoulder straps on the pack are meant to wrap up a little bit and then go over your shoulder. The load lifters are pretty effective due to the rigidity of the backpanel. The pack uses a single stay.
I don’t know about the current HMG hipbelt pockets, but the Onni’s seem bigger than the old HMG ones. I guess the Onni’s are large, in the sense that they run for almost the whole hipbelt length, but I just wish they had a little more volume.
I’m pretty sure Katabatic Gear’s Liteskin Fabric is this LS07 (not related to Cuben Fiber):Â https://ripstopbytheroll.com/products/liteskin-ls07
The pack is not seam-sealed, and the bottom is actually 500D Cordura. I like the Cordura bottom, because one problem I had with my old HMG pack is that water would just pool at the bottom.