As for the down, if its like a sleeping bag that compacts easily, I can't see the benefit. I carry a downbag and half the weight of it is compacted to nothingness beneath me. Maybe a top bag next time.
Its not like a sleeping bag and the down is uncompressed. If you are feeling you are carrying too much weight in your down bag you should consider a down quilt as you dont get the compression below the body. I thought you didnt use down though as 'it rots away'
