Z packs Arc Blast

I have the 60l Arc Blast and the main body isn't all that large.  My 55l Gregory pack has a larger main compartment.  I think a lot of the measured volume is in the side pockets and mesh pocket.  I'd get the 60l for the times you have a lot of food or something else bulky - You can always not compress your quilt very much and tighten down on the side straps when you have a small load.

I love the side pockets on the Arc Blast.  I can easily get bottles in and out while hiking, but the elastic is pretty good at keeping stuff in.  I ordered one hip belt pocket and it is very roomy and convenient too.

Sounds like you use an ursak, but if you ever need to carry a bear canister it's a bit finicky to fit in the pack.  It needs to ride in the top half of the pack, vertically, above the middle horizontal bar on the frame.

I love the pack for <25 lbs, no bear canister hikes.  It's very light, I like the airflow on my back and the design of all the pockets.  It sounds like it would work very well for you, given your parameters.

I have the Arc Blast 52L, it's the 2014 edition so does not have the adjustable shoulder strap / torso height. Otherwise the bag is pretty much the same as the new edition.

I love this pack. It's comfortable but not "cushy". I've used it for 7+ day treks with a Garcia bear canister and was never tight for space (could still get 3 rolls on the top closure), yet for weekend overnighters without the bear can it's still fine just cinched down.

I ordered mine with lumbar pad, load lifters, two hip belt pockets, and no hydration port and am pleased with all these choices. I definitely suggest getting the lumbar pad, without it you might feel a hollow at the bottom back of the pack. The load lifters on mine don't attach to the frame so they really are more load cinchers, but they bring the top of the pack in closer to my shoulders and that feels a lot better to me (I think the updated version the load lifters do attach to the frame but not sure about that).

The hip belt pockets are huge and bulge out pretty well when full. At first I wasn't sure about them but have come to really like them -- my former pack had several pockets that the Arc Blast does not have, and all the ditty stuff that would have gone into those pack pockets now go into the hip belt pockets. I really like having all those things at my fingertips, without having to take my pack off. Camera, PLB, FAK, repair, headlamp, headnet, pencil and pad, permit and ID, snacks and more are always accessible on the go. I've attached the pockets as far to the front of the hip belt as possible so they are not in the way of my swinging arms. If you're getting the multipack you may not need the storage offered by both or even one hip belt pocket, but if so my preference would be to wear the multi as a chest pocket rather than a lid.

The Arc Blast is essentially waterproof, being made of cuben with taped seams and a rolltop closure, so my stuff has stayed dry through downpours without a pack cover or liner.

I agree the side pockets are relatively easy for water bottles on the go.

Keep in mind that the difference between the 52L and 60L models is the depth/circumference of the pack body, both models are the same height. So with the 60L the weight will be slightly further off your back.