Hi Hacksaw,

I've just looked up the specification for the The North Face Aleutian Sleeping Bag, which is rated at -7C, which is a 1545gm synthetic bag . I don't think this is going to warm enough for the temperatures you have indicated. The -7C or 20F appears to be the extreme temperature range indicated on the US TNF website information. The comfort range is 2C on the UK websites. i.e just above freezing. I could be wrong but the TNF website doesn't appear to indicate what temperature the -7C refers to, whether this is the comfort or extreme rating. If it is the extreme rating then this would be the temperature where there is a risk of cold weather injury for the user.

http://www.thenorthface.com/opencms/opencms/tnf/gear.jsp?site=NA&model=AZG7

If your expecting -15C with possible windchill effects combined wtih inadequate wind breaks from the sil poncho tarp, real temperature effects could be approaching -25C in a moderate wind i.e. 15 to 20 mph. You could be risking a cold weather injury.

You may also have to come up with some novel ways to keep your gas cartridge stove working at these temperatures as well. You will need to ensure that the gas cartridge does not become chilled or the stove may begin to stop working even when the cartridge seems to be still 3/4 full.