On a few trips lately I've actually gone in the opposite direction....instead of using clothes as part of a sleep system I use part of my sleep system as clothing. I use an Exped Wallcreeper (now called the Dreamwalker)as a jacket. It has a full hood and arm holes on the sides. It's a blanket, a jacket and a sleeping bag. Quite versatile and better suited for the hammock I find myself using more often lately.
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If you only travel on sunny days you will never reach your destination.*

* May not apply at certain latitudes in Canada and elsewhere.