I just spent my first chilly night out. I put a tapered synthetic 0* sleeping bag under me in my diy tbcf hammock with a 20* unzipped mummy down on top and slept warm as toast at 34* F with 15k wind. no tarp, no dew or rain. slept on the bag zipped up so it was double thickness.
next i will try just the 0* bag alone unzipped.
i am a still sleeper.
the only negative i see is the weight and bulkiness of 2 bags.
i do plan to make an under bonnet from a quality bag or mummy,
the two i have now are just too fine to cut up.
just thought some other nubies might like to think on my experience.