"With your 9.5 lbs base, that works out to 1.16 lbs of food per day and no water, or 0.9lbs of food per day with 1 liter of water. Are you sure about this? Or does the "~20" mean your pack is actually at more like 25 lbs?"
Relatively sure, Dan. If you think about a 9 day trip, it requires 8 full days of food and a lunch the last day. This year I carried 19.4 oz of food/day plus 5 oz of Perpetuem for lunch the last day. Check my math, but I think this works out to 10 pounds and .2 oz, which I will call 10 pounds for all practical purposes. This actually works out to less than 20 pounds, 19 pounds 8.2 oz to be exact, but I called it 20 out of laziness. As for water, the most I ever carry is on the first leg of the Shepherd Pass Trail, 3#, so I would be at 22.5# starting out and down to 19.5 after about 5 miles. After that it is usually a pint, so that would make it 20.5 and falling for the rest of the trip. Any other trail I use these days would see me starting out with a quart at most, probably less, or 21.5#, max, more likely 20.5#, or even zero if water is plentiful, like on the Paiute Pass/Lamarck Col trails. I'm not a gram weenie, but neither do I carry 25# and "round it down" to 20#, Dan. Water varies all over the place, so I didn't include it in my calculations.
Edited for intemperate language. Apologies to those who read this before I cleaned it up.