Spent my evenings this week making the pockets for the rucksack. I used much the same technique so, basically, I made two tiny rucksacks - about 3 litres each. They, therefore, give you the option of bringing the capacity of the rucksack up to about 36 litres and the total weight up to just under 4lbs:
An empty pocket:
They attach to the rucksack side straps via sleeves sewn onto the back:
To make it look like this:
Modelled by me:
Hoping to get out into the woods to do a field test in the next couple of weeks. I will post a review when I do. In the meantime, got to get on with those jobs I've been ignoring in order to get this finished...