I've been DE shaving my head for about/slightly over a year now and typically use either a '60s gillette tech or a modern merkur 37c slant but I have also used many other DEs on my head as well. I've consistently found that if I ever use the 37c with anything less then 2 days growth or use the 37c for 2 or more days in a row I always get ingrown hairs and bumps on the nape of my neck in the back. I always read Slants help to reduce ingrowns and when I (rarely) don't sport a full beard I've found the 37c to be the only razor to give me a smooth neck and atleast much less ingrowns. Any suggestions or does this happen to anyone else? If this helps: I shave almost daily, in the shower, always an omega synthetic brush, rotation of soaps typically including Proraso and Arko, always do a final cold water rinse, always apply witch hazel, and always use an alcohol based aftershave.