I also have exactly the same stuff for a longer trip; the only increase is food and fuel. Even for a 10-day trip (the upper limit on weight for me at 26-27 lbs.) everything fits in a 2400 cu. inch pack plus outside mesh pockets.

I too may take a little more for a 1 or 2 night trip, usually a larger tent, especially if it's a base camp type trip.

Even with a bear canister and hauling grandkid stuff, my pack contents have never overflowed into the extension collar of my pack.

To the OP--You might want to check out the articles on the home page of this site, left hand column.