years ago i bought a couple of head-overs at silvermans,they were O.D. wool and could be rolled into a capcomforter and it was told to me from the clerk that sold them , you could sew the tube shut to make a capcomforter...
I tried that when I first got a headover. Fact is that they are smaller than the cap conforter - shorter that is if I remember rightly, so it doesn't work, or at least it didn't for me. You can end up with something you can put on your head, but it isn't the same.