Half helmet? I know it's a Harley thing (I never see Harley riders wearing a real helmet, but I do see quite a few of them gritting their teeth while they freeze their asses off), but it would suck to wake up in the ER to find your lower jaw missing.
As for loud pipes, mine save a lot of lives. I bought them because my stock pipes fell off. The Cobras were the lightest and least cantilevered aftermarkets I could find (not many choices for my bike), so I figured they'd at least stay on. They have, but unfortunately they turned out to be twice as loud as my originals. I might as well just go with it and get an air horn.