Now that we have the new Triple Cross stainless frames in stock we pulled one out and threw an IRD B76 caliper on it and voila! It works.
The pads are at the very bottom of the slot, so other brakes like the Tektro R559 which have a shorter reach probably won't work for this trick. Now before the disc brake mafia get's up in arms about stopping power, we know okay! You'll get better stopping with a disc brake than a super long caliper. But somtimes there are situations where you have all the parts from another non disc build and you want to get it finished and this trick will make it all come together. IRD sell this brake singly so no need to buy an extra if you only need the rear.
The brake bridge even takes a recessed brake bolt, so no need to worry about using a nutted caliper.
FYI, if you like this setup, but you want a little more stopping power the new Dia Compe 750 recessed centerpull brake should also work if you use a cable hanger mounted to the seatpost binder.