Has anyone used any of the helmets with the so called "chin diffusers" that are supposed to keep air from blowing up under your chin. I've noticed quite a few helmets claim to have this feature. HJC AC-12 is the first one that comes to mind, but I know I have read the same thing on some of the Arai's and Shoei's. My chin is the only thing that I can't seem to keep warm when I ride in cold weather.