Consider a Natural Alternative, Wool.
This link may help to see what the complete sleeping system looks like.
http://www.ebay.com/itm/CZECH-ARMY-...s=63&clkid=5850676553400420940#ht_1769wt_1259
I have no experience with what you’re inquiring about because I personally don’t like synthetics. I do not find them very comfortable. I do not feel that they work as advertised when wet. Then there’s the heat from an open flame issue, open flames themselves, and sparks/hot cinders to deal with.
In 1984, I got sick of the intermediate bags they issued us in the Corps. I went off base to Saigon Sam’s (military surplus vendor) for a WWII 100% wool blanket. We were issued wool blend blankets, and it was suggested to me that I go out and buy a 100% wool one. It was there that I spied and old 100% wool WWII sleeping bag, and I thought that in combination with a 100% wool blanket would be the right ticket for days, weeks, and or months I spent in the field during North Carolina wet rainy winters and very damp air.
It worked like a charm. Since I don’t go out humping on 20-mile force marches, I don’t mind the extra weight of the bag and a blanket. For me, it’s worth the extra weight when carrying comfort gear.
I’ve seen these bags going for 20 – 30 dollars online. The thing I like about it is that it’s American made, so it’s designed for people up to 76” / 193cm tall. I’m 6’3”/1.9m tall, so most military surplus blankets are a tad too small for me to wrap up in properly. Moreover, I used to have to keep my rifle, boots, and clothing inside the bag with me because we didn’t have fires to stay warm. In the civilian world, this isn’t an issue, but it’s still nice to have a large roomy bag that I can put hot rocks and or water bottles inside the bag with me.
I’d suggest a wool bag if you want a piece of dedicated sleeping gear. It works nice in conjunction with a 100% wool blanket.
I’ve included some photos of my old bag dated 1944. I’ve put a Mora in the foreground for scale. It’s slightly smaller than a 100% wool blanket when rolled up.
There’s always the alternative. You could fasten snaps, a zipper, or buttons to a wool blanket so it could be converted into a sleeping bag without losing it’s ability to perform as a blanket, poncho, and the like.
http://www.armynavysales.com/products/ww2-wool-sleeping-bag-liner/
http://www.sportsmansguide.com/net/cb/used-us-military-wwii-sleeping-bag-khaki.aspx?a=772985
Good luck with whatever decision you make.
Cheers
cheap'n'squeaky