About 20 years ago a guy named Ranger Rick was converting poncho liners by sewing a zipper on three sides so it would close up into a roomy sleeping bag. He also cut a small line in the middle for the head so one could wear it as insulation and had a zipper sewed there to close it while using as a bag. The kits to do this might still be available. I still have it. Wouldn’t want to put a non breathable poncho over because that can cause condensation. Tried it with a silnylon tarp and condensation was bad. The poncho liner itself is good to about 60°. It’s a summer bag for the most part in most areas. It’s heavy for what you get. I I’m remembering right it’s about the same weight as the 20° down bag I use.