I read a story somewhere that a helmet was stolen by a scooter rider. #
The helmet was locked in the bike's helmet lock by the 'D' ring of the strap.
The thief simply used a knife and cut the strap, and made his escape on his scooter with the lid.
I have made up a small chain/padlock combo and that goes around/through the Tour-X and then around the rear rack on my GS. Although it could still be cut, it would need something heavier than a penknife to do so.
Timpo.