I know it's heretical to argue with Sheldon Brown, but the issue that I have with his locking technique isn't that it wouldn't work, but I think part of a locking strategy is deterrence to anyone who would think about stealing a bike. I'm not certain that just locking through the rear triangle would signal to someone that the bike is securely locked, so I'm thinking that someone may see that and try to break the lock.

Not sure if this actually happens, though.