hey folks, thanks for the suggestions. i'd considered a very light down blanket and may do that. the poncho liner sounds like a great place to start - something i hadn't considered at all. thanks much.
something i'm going to experiment with - microfiber. i have a friend thats one of these guys always running up on a deal. well, he was driving by a cut-and-sew near the gulf coast the other day and they had a special - bolts of microfiber cloth. anyway, he snagged some and told me about it. i'm going to cut a section and try it as a blanket. i'm sure it's fairly heavy, but on short overnighters it should do fine. i'll report on this when i can.
thanks again for the poncho liner tip.