Where do you guys put it?

In that locking thing above the chain, wont it hit the chain? how would I lock the strap?

 

If you still have the passenger grab strap you could thread the helmet strap thru that and hook it up like it was on someones head. That should keep it high enough that it will not interfere with the rear suspension and such, or buy a bungee net ($5 at most shops) and strap it to the rear seat that way or you can use both methods

 

dont have it no more i cut it off