I usually use a GG G4 backpack for long-distance trips and I am very happy with it. But when I tried to pack it for my first long winter camping trip in years I had to realise that it is just too small for my winter gear. Weight is not the issue here as my winter base weight ist only about 1,5 kg higher than my normal 3 season base weight of 6 kg. The problem is volume: My winter sleeping bag alone, a WM Puma, is so bulky that it almost completely fills up the GG G4. Add a thicker sleeping pad and some more winter clothes and the G4 turned out way too small.
Instead I had to use an old Golite Gust that has unfortunately been discontinued. The Golite Gust has a capacity of 4,600 c.i. (75 l) and is just about big enough. As this old Golite Gust is almost falling apart I will soon need a replacement, but all the UL backpacks that come to my mind are far less voluminous than that.
Any suggestions for UL backpacks with a volume of at least 4,600 c.i. or 75 l?