In reply to UKH Articles:
"With supplies for a night or two this lot should squeeze into a medium sized rucksack of about 40L."
hah! whatever rucksack size you choose, you will fill it.
Don't forget your bulking factor:
suggest 20% general,
additional 20% when raining
for those that don't know:
bulking [ˈbʌlkɪ©¯]
n
1. (Engineering / Civil Engineering) the expansion of excavated material to a volume greater than that of the excavation from which it came