I’m working in the Everglades this spring and looking to mod my sleep system.  My experience there in December was my down bag seemed to absorb moisture overnight.  We often sleep out or under bug nets instead of tarps and I use a bivy to reduce all the overnight dew.  Not sure if the moisture absorption was from me or the outside.  Anyway, I’m looking for a light synthetic bag in a long size (I’m 6’1″ and 200#), and I’m also looking to experiment with adding in a silk liner, and I’ll use the bivy, bag and liner in various combinations based on weather and humidity.