Ah, I was hoping there was a cheaper option. Not sure the tri-rig is worth the $ since most of the aero goodness is hidden under the shroud. Wonder if a Campag rear TT brake could be configured to work? They're only ~$40.
That bugs me too. Testing is limited so far but what has been done shows that the bottle is far more significant than the marginal gains from the centrepull caliper. So it makes a lot more sense to go with the bottle and a cheap brake that doesn't block the gusset. Unfortunately there aren't any cost effective front centrepull calipers now - I can't recommend putting rear brakes on the front in order to use PD product.
Will see if I can find a Transition to test on as that would answer the question in a safe way.
Did you ever happen to find a Transition to test on? I have a 2013 Transition that I'm thinking of upgrading to an UA and wanted to make sure everything would fit before jumping into it.