I actually just used a 3 season down bag.

I was needing to keep my pack real light so I used a base layer of capiline or thermax for warmth because I could use that during the day too if I needed to.  I also had a fleece hoodie available.  One thing about those little one-man bivys is that the fly will hold in a lot of heat.  I was very comfortable.

I use a North Face Quartz 22 tent. Its nice an lite at 4 lb and gives you a little more room than a bivy. You can fit two in but it's a little snug. I looked at the bizy to use but didn't think I could handle being strapped in that tight plus you have no where to store your gear if the weather is bad.

For my “Bivy” hunts here is my list.

1.       Is my can’t live without Eberlestock just one backpack with the supper spike duffel and water blader.

2.       Marmot Hydrogen sleeping bag

3.       Coleman Avior x2 tent

4.       Them-a-rest z-lite sleeping pad

5.       Energizer head lamp

6.       Snow peak Titanium cookware and stove kit

7.       Katadyn vario water microfilter or 3 liters of water per day

8.       MREs to eat

9.       Clothes

10.   Hunting gear (bow or rifle)

Depending on how many days I’m gone my pack could be up to 75 lbs.  Depending on the area you go into and the water availability there you can lighten the load considerably by using the water micro-filter instead of packing in tons of water.