ummm… no. Well, thats my opinion. I use a 38* down bag for summer hiking. Every now and then I will don on thermals, even through the summer. I do understand your theory of layering, but I think youre selling yourself short and will probably freeze your ass off. Personally, I have a summer bag and a winter bag. I believe this is the way most people do it who camp 3-4 seasons of the year. My winter bag is a Moonstone 10* down bag. Ive never been happier or have slept better than in a down bag. I had been using a synthetic bag for 5 years before making the switch. I never really had any complaints from the synthetics, but I didnt know what I was missing.
The down seems to breathe better at night, so I dont get overly hot/sweaty. Its an ‘airy’ warmth feeling thats hard to explain and can only be experienced from getting in a down bag. Then theres the super-light/compressable factor of down products. Thats always a plus when keeping your load light.
The only reservation I had about down was the age-old question… what happens if it gets wet, I’ll freeze my ass off. Well, perhaps down from the 70’s or 80’s… or perhaps early 90’s was that way. Most of the bags I see today have such a good shell, they just cant be beat. Before I set out on a winter trip I poured a nalgene bottle of water onto my bag, as it was set up on my livingroom floor. I let it sit there for quite awhile. I watched it as it just set ontop of the bag pooled, but never soaking into the material. I then wiped it away, thus pushing the liquid onto the bag. After I wiped it up I got into the bag only to discover the water didnt premiate through the shell at all and the bag was very warm.
So, I suppose what Im saying is that Im a huge fan of down. The manufactures I would suggest for bags are: Western Mountaineering, Marmot, Moonstone. There are others, but these have my votes. Spend the extra money and get a nice bag, youll be glad you did.
guru