After spending a cold fall November night on the Appalachian trail during a short 1 night section hike I did some reading and thinking about how to improve my shoulder season cold weather hammock gear. I ended up getting two items. First a Dutch cold weather sock to block wind all around my hammock. From all reports that will give me maybe a 5 degree boost in felt temp. I also got this rectangular down sleeping bag that would allow foot movement but also can be snugged up around my head to eliminate drafts. So far I have spent several nights using this bag as reported below.
The first night, I tried them out in 45F temps and slept great all night. I was neither overly warm or cool. That night I wore jeans, two pairs of socks, a long sleeve shirt and a polyester fleece jacket with a stocking cap on my head. I had available more clothes but did not need them. I could have added another leg layer, shirt, scarf, gloves. I did end up pulling the sleeping bag over my head to keep my face from being cold and that worked good and was comfortable. I didn't do anything to snug the bag up around my head as I was not troubled by drafts. I did use an inexpensive 1 season hammock under quilt which does not work great with a diagonal lay but my feet were warm in this bag even though the under quilt was not all the way under them.
It was a struggle to get into the bag which was expected. However, once in it I was comfortable and was not troubled by drafts which were a problem I have had with a separate top quilt. I seem to like to sleep with one leg bent and that pulls one foot out of the foot box and also tends to cause a draft that wakes me up occasionally during the night. Also, my foot gets cold easier if it is not in the foot box. The enclosed rectangular sleeping bag did not have that issue and allowed leg movement. If the night time temp is expected to be in the 60s then I will still use the top quilt because it is more convenient and less challenged by those temps.
The second night I was chilled under the same conditions. After some consideration, my thought was that breathing into the sleeping bag caused moisture to accumulate that reduced the bag's insulating properties.
So prior to my third night sleeping in this bag, I got a light merino wool balaclava. Last night I established a new personal record for cold weather hammock sleeping at 36F and I felt fine. I wore a few more clothes and kept my mouth outside the sleeping bag so I did not breath moist air into the sleeping bag. That also allowed me to close up the sleeping bag opening more using the drawstring so I did not get drafts.
I had on 2 pairs of loose heavy socks, two leg layers (tights and ski pants), three upper body layers (long sleeve polyester tee shirt, sweatshirt, light fleece jacket), then two head layers (balaclava, and a toboggan). I also placed a polyester scarf over my face area so I was not directly breathing in cold air. It was hard to get it placed over my face and then close up the sleeping bag but I was able to struggle some and do it. My cheap under quilt does not align with my normal diagonal lay and so if I got my feet too far off the underquilt area they would feel chilled. However, I still like the freedom of leg movement that this bag provides
I am a male, 5'-10" tall, and weigh 173 lbs. I use a 12' long hammock.