You could carry your own chickens and then boil their eggs each day for breakfast before you began walking.... That is, if all the interior space wasn't already taken up with rocket boosters to take you along the way without actually doing any walking....
LOL! Now the question is: water bottle or Camelback?
Seriously, I used a light-but-structured 30-liter Jansport Tree Frog pack on my latest Camino, and I won´t ever use anything else from now on, not even my GoLite. Yeah, its small. But having less volume means you cut way down on the temptation to overpack, because you CAN´T overpack! It held everything I needed, hung close on every curve, and is showing no sign of wear, even.
There´s a reason why so many veteran hikers carry so little weight and wear such little packs.
I've heard stories from other pilgrims about carrying such small packs and I always wonder where their sleeping bags are.
I would love to get down to that size pack, but in May, need to take a sleeping bag. Did you manage without a sleeping bag, or did you have a liner, or nothing, or was your sleeping bag outside your pack? I think I could do it in summer, but since I never walk a camino in summer, never going to happen. Dying to know your secret and those of others who appear not to be carrying sleeping bags in spring!
I carried a small sleeping bag the first half of the camino (a 40F that squishes down really small), then traded it in for a liner halfway. Both fit just fine in the bottom of the bag, with clothing rolled up on top that, towel in its own outer pocket, etc. I think the key was rolling up things and compartmentalizing them, just fitting everything in around everything else. I clipped my sandals and jacket to the outside of the pack with a carabiner when I wasn´t using them. Three shirts, two pairs of pants, three sox, a poncho, sleep sack, bandana, hat, towel, toiletries, maps and diary. Other small & needful things went into a small pouch/handbag worn out front. It worked just fine, and as time went on and I shed more and more stuff I had room to spare.