Unfortunately, with the advent of light, powerful, and portable power-tools any lock or chain is, at best, a deterrent or inconvenience to a thief. For example, last year thieves systematically knocked a hole in a garage wall to steal DH bikes, in our local news area.
IMHO the only solution is enough security to deter a casual thief, and good insurance just in case. A determined thief will either trash everything to get his prize, or mug you for it.