I have been experimenting for a while now and so far, have found a helmet mount to be the most stable. It also gives a better perspective of the road and surrounds. I started off mounting on the crash bar and, while it gives a view of the front suspension working, it is a bit limited, so I guess a combination of mounts is optimal. Currently trying out mounting it on the helmet chin. Here's an example of a shot from the helmet:
Edit:
Sorry, can't load it as the file is too big. I will have to edit.