a lot depends upon time of year, if it's in the winter you need more clothing and a warmer sleeping bag, hat, gloves, long johns, etc. (so more room in your pack).
Also depends a bit upon where you're going, because some national parks in California require bear canisters, so your pack needs to be large enough handle those.
Also, hiking in alpine meadows at 10,000' is much colder in the summer than hiking along a beach.
All that said, I used a Osprey exos, 58 Liter, 2.7lbs, great harness system, especially when fitted properly by REI experts in store. It has met all my needs, even in winter conditions. But, I probably would have a very tight fit if it was dead of winter, 5 days, with bear canister.
Bottom line, I recommend a 58liter pack. I would not go lower unless you're prepared to spend a bunch of $$$$ for ultra light stuff.
Just looked at that pack, YIKES! Super expensive, one of the heaviest! Only a 45 and a 70 liter version!? Probably intended for heavy duty climbing, where you need an extremely durable and roomy pack.