Helmet side mounts are everywhere on Utube. I've seen Vids on helmet mount on the chin works great. But you still get lots of head movement.
I found the best (if you are not mounting it on your bike somewhere) is on your Chest Protector. Always facing forward, no head movement, get to see lots of the bike, standing or sitting.
XC 300.... Chest Protector
GreenStones Mtn.... Side of Helmet
Snow Ride.... Side of Helmet
Scuitto Flats Kamloops .... Rear Fender of Bike