Not for nothing, but the synthetic bags have come a LONG way, and are usually cheaper than a high end down bag. And, they compress pretty small these days too. I used to be a down fanatic, but with the advances in synth, and an unfortunate tear that left me without a bag for several days, I switch to synth.
Anyway, thats my $0.02.

 

My specific recommendation would be a Western Mountaineering TerraLite. Very warm. Packs very small. Super comfy. Holds most of its value long term for resale. Premium bag all the way.

 

I used to wilderness winter camp and I found having at minimum a thin insulating pad under the bag and a Walmart type fleece sleeping bag to use as a liner for my 15 degree rated Cabela's Slumberjack bag has kept me warm into the single digits many times. It's more to carry but I'd definitely recommend something under you. Warm & comfort will cost you either $$$ or space on the bike.

 

 

You've got some good advice here about some sleeping bag choices. Regarding the plan to sleep in a hammock, are you an experienced hammock sleeper? If not, I suggest trying it out for a couple of nights before committing to a long trip with no other options. I don't find them comfortable for all night sleeping. Some guys do. Remember that with the air circulating beneath the hammock you will be colder than sleeping on the ground.

 

I take a tent for when there are no trees... but if I have a choice I sleep in a hammock. Wham... bam... on the road in 15 minutes heading for coffee...

 

That's why I wish I was comfortable in one. So quick and easy. But I feel like I am being folded in half at the shoulders. Maybe I am doing it wrong.

 

I hunt in a fly in camp in the middle of Idaho in Oct-Nov. Cold, snow.

I switched to a modern fiber filled mummy bag several years ago from a quality down bag. It packs as small, is just a few ounces heavier and I do not have to worry about it being damp. I use a light weight fleece bag liner. It makes the coldest nights feel warm and toasty.

I also went with a thicker foam pad. At first, as being older I just need more padding, but I immediately noticed I was warmer at night when it was 20F.

Fit of a mummy bag is important. I am average and my down bag is a standard. When I went to get a new bag, and ended up with one of the new synthetics, I bought a long version. It also had a slightly larger mummy foot area. Wow, what a difference for someone who tosses and turns before falling soundly asleep.

I think rather than recommend the brand and model I purchased, research and jump into them. REI was an excellent source, but I ended up purchasing my bag elsewhere as it was a brand they did not sell. Theirs may have been as good, but it was not offered in a long. The fleece liner is tiny, yet adds so much. The zipper on the fleece feels fragile, but has lasted for years of hard sleeping. The zipper is much stronger than its small size would have you believe. The pad is not tiny, but I need 3" to keep my bones off the ground and it has made a huge difference when the ground is frozen or the tent is on top of the snow.

 

I'm like you, could never get comfortable in one but I haven't had the chance to try this way of sleeping in a hammock, though I'm ready to give it a try....

https://www.treklightgear.com/blogs/.../hammock-angle

 

That sure seems worth a try. Thanks.