Thanks for all of your input - I'm probably going to go to the LBS and see if they have a spare Fahgettaboudit U-lock, and if they will let me try and fit it on a Specialized seat post. As you can see from the picture below, there is very little room between the back wheel and the post:
http://www.paulscyclingfitness.com/C...lez_triple.jpg
If that doesn't work...chain it is.