Thanks. I had a line on some free type 14. And was thinking of some uses for it.
But I lost out on it anyway. Soft structure tyvek is very breathable. Much more so than calendered nylon. Also I was using some scraps from some old tyvek clean suits to practice sewing on. And I noticed it did seam like it would tear pretty easy at the seams. I wouldn't want to have a taped together underquilt.