i don't have a BOB just gear in my PFD i case i get washed overboard and lose my canoe and packs.i expect that i would make a shelter from a foil blanket and branches.i found with some test lashings--i'm a "old scout" and i know how to make simple lashings--that the nylon line that block layers use is strong enought for a simple shelter.a 50 foot hank of this line takes up little space and no real weight.it's easy to cut,you could run it over a sharp rock if you needed too and it comes in bright colors. para cord is good stuff but it sort of got a name as a all purpose cord from it's military days and there is other stuff out there. the only thing i use para cord for is a clothes line...ok--i'm on a roll here...i would skip the para cord in a BOB and take mason's line and real rope,para cord is too "in between"--too heavy for lashing and too light for rescue work or heavy hauling and pulling...