I have been looking at making my own out of Goretex. So far the widest material I have found is 57", so a seam would be incorporated. I have spent more nights under a USGI poncho than any other shelter. I dislike the poncho liner. It provides little warmth and it is impossible to keep in place (slippery). Way too much bulk and weight. A surplus wool blanket of the same size and weight is far warmer, and still works when damp or wet. My experience with this equipment is extensive, as I used it for the 26 years that I spent in the Army.