My only negative comment - and an important one - was the stays. These are not part of the original Blast 22 design, but are optional extras. I have a MLD Burn in Dyneema, but decided to change for the Blast cuben hybrid fabric and get the stays, not for load support (only carrying around 5.5 Kgs), but to keep the bag ridged when packing/unpacking.
This concept works great, but I found occasionally the stays would "knock" on my shoulder blades. I think this is because the Blast 22 has a narrow back panel profile (say compared to the Blast 30+), this puts the stays closer together on a larger male back like mine.
Maybe the pack, not being totally full, pulls the stays in at the top causing them to touch the shoulder blades when swinging the arms when using 2 walking poles? Note the first photo below how close the stay is to the shoulder blade.
I am going to talk to Joe (Zpacks) about whether a spreader at the top would elevate this. Failing that, take out the stays. The pack will still work well, just not "stand-up" when packing. unpacking - Lightweight is full of compromises!
Here are some photos - I note Zpacks website now label this as the "Zero" with options. I opted also for the 2.92oz Cuben Hybrid with side pockets. I added the old hip pockets from my Arc Blast pack, now using the new hip pocket design from Zpacks.