Very envious of your ULF adventures up there--lots to look forward to, I'm sure.

If for some reason you find yourself in need of a bit more in the way of suspension, I'll throw this pack in the mix:
https://www.hillpeoplegear.com/Produ.../ProductID/100
Basically, you could use the Granite Gear pack like an f-stop ICU in the HPG's strap-harness, and then probably find a way to attach a couple of more pouches to hold FAK's and whatever snivel gear you like to take with you. I've owned several HPG packs over the years and have found them exceptionally well thought out, the shoulder harness and hipbelt especially. (That their stays are soft enough aluminum that you can customize them to your lumbar curve can be a valuable feature as well.)