so the higher the fill number the less the bag will weigh and the more it will cost?
Pay more for less, fun isn't it?
You could always buy some down from speers and make your own TQ. Jump in on the down group buy. With a little DIY you could save a few bucks.
Probably said this too many times already on this forum, but I can't help but recommend the Cabelas XPG -40F goose down mummy bag.
Waterproof outer shell and made just as nice (dare I say, if not better than a TNF or Feathered Friends).
Check it out here...
They had them on sale for $349.00 on the website, but it looks as thought that sale is over. If you're serious though, I can see if they still have them on sale here at the Sidney store. Just a thought.
Also, I have a Kelty 50th Anniversary 6000c.i. external frame backpack. Weighs only 6 lbs and fits/feels like an internal frame backpack. Unfortunately, they made them in limited quantities and now eBay might be the only way to get one. But, this is a lightweight U-Haul. It is made for 7+ day pack trips. You can pack it full and won't even notice the weight on your back. Anyways, it is some serious quality from Kelty and weighs less than some internal frame packs. I would have to give Kelty 5 stars!
I think you'll find that the goose down is the best way to go for lightweight/compact:warmth ratio. Now, it's just figuring out how much of a down bag you will really need and use. Plenty of thoughts/ideas/recommendations here on HammockForums.net!!!
My experience from doing a AT through hike and about 500 - 900 miles of hiking a year since. First, a down bag should have 800+ fill - otherwise you're not saving much in the way of weight and compresability over a good synthetic bags. Second, don't be afraid of all the stories about how bad down is when it gets wet. Short answer is to keep it in a separate water proof bag or trash bag and it'll stay dry. Third, get a 15 or 20 degree bag. If you go for a zero degree or less bag, you'll roast yourself in cool weather, but freeze when you try to vent the bag to cool down. Of course, if you always hike in zero or below weather, then a zero degree bag makes sense.
If you want to stay with real sleeping bags, you can't go wrong with Western Mountaineering, but they cost more. If you are sticking with the hammock, consider a quilt like what JacksRBetter offer. I particularly like the No Sniveller bags with the head hole. Really nice for hanging around at a cold campsite.
I agree with most of the comments regarding "Buy A Down Bag," however to respond to your concerns about high humidity and water problems, here is my two cents.
Look into Montbell Super Stretch Synthetic Sleeping Bags (http://www.montbell.us/products/list.php?cat_id=31). These bags come in a wide variety of temp settings: from 0 to 50 degrees.
Also, if you (like me) do not like the confined feeling of most mummy bags---I toss and turn at night and really do move around quite a bit--then the super stretch feature is really the bomb. These bags feel as if nothing is on you...and your movements are completely unrestricted!
As to pricing, I have found deals on the Montbell bags; more often then not on Ebay (for lots of reasons, I do not recommend buying used sleeping bags). But, search the Internet and you can find some smoking deals.
BTW, Montbell bags have a life time guaranty.