I'd not say completely paranoid - I *have* had platys start to have a slow leak in my pack, although it's been due to wearing out not being poked by something in my pack. - and a canvas pocket would not have helped.

My solution to that paranoia is I take two platys - the empty one weighs less than a canvas pocket, and if one *does* get a leak, I have another - and normally I have two to fill in camp so I only have to deal with filling water up once when I stop, so it's weight that has multiple uses and gets used.