If you want to premake it, look for 55 gallon liners. I can curl up in one, and not much about me is dainty and petite. You might find they work as is.

And if you are relying on something like this, you'll want to curl up to conserve body heat.
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-IronRaven

When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.