Problem with the comforter approach is that most comforters made for in-home use have cotton shells. This will just soak up moisture in the damp SW environments. I think if you look around you can find a fair synthetic sleeping bag on sale in the $60-80 range. With warm temps, you do not need much so should be able to find a 40-degree bag that is under 3 pounds. When I was broke and needed a bag I bought a cheap dacron fill 0-degree Slumberjack bag and it kept me warm- made me really appreciate my down bag when I could finally afford it - how nice to go from a 4 pound bag to a 2.5 pound bag! I also had an external frame pack - in this case just buy a bigger stuff sack for the sleeping bag! No problem.