You overlooked the fore runner of the bivy bag hiker. The cagoule was what the alpinists used first. I myself don't have a problem with carrying a two pound mummy rated to 23 degrees and a cabellas bivy which wieghs under a pound. It's a warm combo. I also have a kelty down mummy that's rated to 25 degrees and is extremely compact. Once I had to put the kelty in a space bag but used forest duff as insulation to lie on.