When I was looking for copper, people usually asked back if I can use brass INSTEAD (more common and easier to find among machine shops). No confusion here about it, I think.
How hard is to get the hole tappered right, to keep the tapper straight while inserting it into the hole? You have only one tapper or they came in set of three (I mean same dia, but first tapper cuts shallow tap into the hole wall, second a little deeper, and the third is final?)?
What's the ID of the barb? If you have 12 mm dia hole for barb, I assume the barb would be 8 mm or 10 mm ID?
Did you lower the rpm on a drill while drilling with such big dia bit?
Wanna know! Wanna know!
Great!