My helmet cam is an original Contour Roam ($99 now) I have it set on 720HD which films in 170degree wide angle. Then I upconvert to 1080HD when editing, which you can see on my youtube channel.
I use a zip tie to hold the back end down so it points correctly, and I use the furnished tape mount that came with it. Here are a few pics the event photographer snapped of me when I was in the open for about 2 minutes the whole day!
You can see the mount real clear in this one. I use a Flex 8 full helmet from way back when they were full camo years ago.
The key is to mount the lens between your eyeballs, as you lean out enough for both your eyes to see what you look at, and if you put the lens between your nose and your non shooting side eyeball, it is perfect to capture that "first person" perspective, without getting a ton of hopper. Course having an offset hopper like an A-5 helps as well...