In addition to what others have said, I would be mindful of the chaffing and rubbing on that spot. If your head is like mine, right where your neck meets your head creates a skin fold when you tilt your head back at all. When the skin folds back on itself it can rub together and get irritated that way as well.
When I first went sly I went for a very long run and this area was actually rubbed raw by the end of the run, enough for a decent scab to form afterwards. If I am running long now, I put some Vaseline back there so it doesn't cause any chaffing. I think you are still a relatively new head shaver (like me) so you might need to watch this area for a while until your skin adjusts. Keep it well moisturized and watch any rubbing.
