If you can, the side rail mount is optimal. I have the gun rail mount attached to the left side rail mount of my helmet too, I just don't have a picture with that side showing. You can also to mount it on top, using the velcro with a cord like Noble suggests just be prepared for it to be very awkward quickly accessing the on and off slide with anything that covers it. Also if you get a contour mount be sure it is version 2 or higher, in the version 1 mount the camera does not fit snug and the camera rattles a bit and the sound is picked up by the mike.