I use one on the AT, they're ok. Personally, I would use those as a pattern and use tarp/tyvek to make better ones.
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L.S./M.F.T.
"Once a man has seen society's black underbelly, he can never turn his back on it. Never pretend, like you do, that it doesn't exist." W. Kovacs
"Seek not the favor of the multitude; it is seldom got by honest and lawful means. But seek the testimony of few; and number not voices, but weigh them. "- Immanuel Kant