For any place I expect to have to survive-fish, #10 Tippet material (from most fly fishing shops) is perfect. It comes on a spool, usually. You can pull out (waste) as much as you don't want to carry, then trim down the spool. Some would say that you can use even lighter material than the #10.
I also carry 25-30 yards of 50# test Spider Wire. I know there are pros and cons for this (yeah, I read the threads in this forum), but I find it strong enough to do many of the things paracord would do. Lashing, fishing, laces, patching, etc. Here's how I carry it:
I took the Crickett lighter from my PSK and temporarily hot-glued a short dowel to the base. Put it in a drill chuck, spun the lighter, and tightly wound the Spider Wire onto the lighter. Then secured the tail end with a dab of hotglue. Takes up very little space, and this stuff is scary-strong!