Actually it can be done either way. You can file(or Machine) the cam angles into the Lumps first and then match the underlever to it, or you can file(or machine) the angles into the Underlever first and then fit the Lumps to it, or you can do it the way I did and fit both parts at the same time. There's no particular reason to do it one way over the others as long as when you are done you have a full contact mating surface on both parts that pulls(cams) the barrels tight to the watertable/face.

Colin