So, my #hydration backpack arrived today.
I've adjusted it, so it fits nicely, removed the elastics that came with it for holding poles and the bladder has been washed and is drying in the kitchen.
The acid test will be taking it out for a run, and seeing how it feels, with my bits in it and getting used to being a dromedary.
The bladder that I got, holds 2 litres of water, I will likely only half fill it, not that i'll need that much, but mainly to see what that is like.