That was the original job of the "Helmet hat" with it's chinflaps. The head band was to come out and the head harness loosened to allow correct wear with the steel helmets. I had one for years that came from Ft Wainwright but of course it now has been superseded by civilian life. The Balaclava inside the steel pot was terrible, unless worn without any head harness at all. The helmet with removeable head harness was never made into an M1C version that I saw.