General: How long of a rear brake do you need on your pake's?

I have one of the earlier Pake frames with a soma fork. It's one of the frames that came with the 26.8, externally butted seat tubes. I decided to try to put a rear brake on it, and noticed that only one of my old long reach calipers would even reach the rim. Anyone else deal with this before? Did they used to make them like this, or was my frame just messed up? It's the smallest frame they make, so it's not like they would've had any skinnier brake bridges just sitting around that they acidentally stuck in there.