I made one a couple of years ago using Kdawg's video and Derek Hansen's instructions as a guide. Here's a link to the video:
https://www.youtube.com/watch?v=vsWOelVXuoI
Just don't expect too much out of it. I was hoping for 40 degrees, but realistically more like 50 is as low as it's going to go. It was a good learning experience in that it taught me about primary and secondary suspensions, underquilt adjustments, sealing the gaps and in general how to hook up and use an underquilt. On the pro side, it's cheap and relatively quick to DIY one. On the con side, it's heavy and not particularly effective, though that may depend on the quality of the poncho liner. Not all are equal.
Since then I've had much more success using my poncho liner as a top quilt in warmer weather, or draping/shaping and using it as a pseudo pod in combination with underquilts and top quilts to push lower temperatures. So I'd say a poncho liner is useful to ADD insulation to other systems but not so much a viable solution by itself other than in late spring and summer.
Cheers.
Bookmarks