to be honest i dont think posting a how too is a real problem, if someone wants to open it they will, i remember back in the mid 80s loads of kawasaki 750 were getting nicked. The way this was done was actually quite simple, the culprits were targeting bikes that were often parked in the same place day after day. one of the crew would simply unbolt the helmet lock (this was a small barrel type lock with a bar attached and would simply hold the strap of the helmet, it was operated by the ignition key), it was just bolted on. so the helmet lock and the ignition including the steering lock operated off the same key, they simply had a key cut to suit the now removed helmet lock. most owners would never notice the missing helmet lock as they dont really get used (helmet fills with rain if its wet), then they can just take the bike at there leisure. quite log winded really but then the bike would be worth it just in parts, your boot however is a different story, if someone is breaking into your boot there only interested in its contents and would simply force it open, however if i find a small hole in mine i will let you know
oh yeh and just for the record - the only thing in my boot is the tonneau cover, thats not counting the explosives i have attached to the inside of the boot lid, directly behind the bmw badge