Varonha custom frame... And other ongoing stuff

May I says one thing?

This is your custom build, I would go crazy over small unique feature that you can't get with OTP/vintage frames, I feel that it's a bit of a setback if you went full carbon and end up putting the Surly hanger on it.

Maybe put a little bridge on the seat stay for the cable housing that go through the seat tube? I wonder what the implication of not having the cable straight to the cantilever?

the other way is to mount the cantilever on the inside of the stay, thus allow more clearance with saddlebag/panniers;