My current backpack is a Granite Gear Stratus Latitude which is 79l and weighs about 2.2 kg. I haven't bushwalked for quite a few years, preferring to tour on bicycle/bikepacking. Anyway I have decided to mix things up a bit and add some bushwalking back into the mix. Mostly trails here in WA with water likely to be available at the end of the day.
My best calculation for my bikepacking setup is around 70l capacity which allows for carrying water for the day, around 3-4 litres plus bike maintenance kit etc.
My initial thoughts are a backpack around the 65 l mark for five-day walks. Maybe something like the Opsey Eros which is 61 litres (1.34 kg) in the large size (the question being can I get down the small ...) or maybe the Osprey Atomos AG at 65L (2.18 kg) which puts me back in the Granite Gear league for the weight. That said I'm not that keen on Granite Gear design. It was a freebie when I got it.
Thoughts? Suggestions?