[bobthepanda]

I have a hard time imagining this. To the front or under the bag? Also, wouldn't it just bang into you as you walked?

[imron]

If you are wearing the backpack with both straps, then I attach at the bottom of the strap, near the waist.

Yes it bumps in to me but not in a way that bothers me (it’s more ‘resting’ than ‘bumping’).

[kfarr]

Yes (you can do either or even some bags have a strap on top for hanging on a hook and you can clip the helmet to that) and yes it bangs into you when you walk.