I have a fstop Satori and have friends using all other models as well. Great packs! Unfortunately all its models come with one-size only. It would be perfect if they can offer multiple sizes.
I am using its medium size ICU to carry my Bronica ETRSi system, one body, 4 lens (40, 75, 135, 250), 2 backs, spot meter and all the filters I need. It is hard to believes how much it can carry until you try it out. It works best with its own backpacks as you don't have to take the ICU out every time, making shooting process more easier.