If you use Sheldon Brown's locking technique, you simply lock the rear wheel within the inner triangle to an external object. The question is, what do you plan to lock your bike up to? I tried a Mini and didn't like it because it severely limits my locking options. I settled on a Kryptonite New York Lock (standard size) + cable to lock the seatpost. Works for me.

Update: just noticed you are posting about the Bulldog Mini. My "Mini" was a Kryptonite NYFU Mini. Not sure if dimensions are the same