I have a fair bit of experience of sleeping under a coat <img src="images/graemlins/grin.gif" alt="" />. You can actually stay quite warm like this. I did it by having my feet in my rucksack and the coat covering me. Not exactly luxury but you can get a relitively good nights sleep. It doesn't protect you from the rain though. You can use the lightweight polyester (or whatever) poncho. This is the combination that I carry.