The 550 cord is definitely a keeper, and the dacron line would be a nice compliment to it; strong enough in its own right to be functionally desirable, not so bulky so you can keep 50 yards in a pocket for edc. I have 550 in my BOB, and the dacron in my edc (and more now in my BOB as well, all 120 lb test, about the diameter of dental floss).
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)