Thanks everyone.

I don't think I could make calipers work. There is no where to mount them them on the back. In fact, even using cantilvers will take a little bit of rigging to fit the back. There is a braze on on the bridge as you can see here:



But I would have to use a housing stop as shown below or something similar and it would make a long exposed cable. The Surly stop would work well but would need some mechanism to insure that the loop stays in place at the braze-on. Seems like the travel agents might be the way to go.

We just signed up for our first multi-day ride, the Tennessee Tandem Rally in June, so I want to get everything lined out before then.