Man I made so many measuring errors, sewing errors, and about anything else I could mess up on my bug bivies. If anything else I learned that noseeum is really forgiving and it is pretty easy to cover up your mistakes.
I think my next bivy is going to be clean and simple. Half noseeum and half 1.1 DWR ripstop. On the hot nights the ripstop will be ontop, on the colder nights I can put the ripstop on top. I may use a drawstring at both ends like you suggested to make it really easy.
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