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I agree.

But to answer the OP, is there a cheap reversible way to use an old sleeping bag as an UQ?

oh I'm sorry I meant quilt or sleeping bag as per the OP's original question. I don't think putting them in a double layer would work well.

Can you actually stuff a down UQ in a double layer? I imagine it would compress the material immediately.

Might be a little hard to readjust in the middle of the night. Also, you may want to go for stretchier mesh than not. It may be lighter to just make a DIY mesh hammock with stretchy mesh/netting.
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