I had a helmet stolen off a previous bike (cut strap) so I try to minimize the risk with these helmets. The marine grade stainless steel chains either connect through the chin of the Shoei or the open face of the HJC to the Kijima , or the open face directly to the Kijima, OR either helmet to the rear hand rail of the Vitpilen. Their also good to thread through one sleeve of leather jacket and connect to the rear hand rail....kinda mix and match.
Having said that I still don't leave anything on my bike for long periods and try to keep it in a secure location.
Lets face it, if a determined thief is persistent ???
PS. i don't advertise the fact that the flip Shoei is a Shoei (out of sight out of naughty mind)