One thought on the cable tie idea. I use them frequently working on my cars and I also like to snip off the extra after the tie is tight. I have cut myself more than once on the remaining trimmed stub from a cable tie, they're really sharp. If you want to use a cable tie with a tarp I'd suggest rounding off the sharp corners with an emory board, sandpaper or a file. Otherwise I could see it poking holes in your tarp (would ruin your day) in the stuffsack.
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