I like to install rear sights as you have shown...raise the barrel steel with a cold chisel and file for perfect fit. This system has several advantages to just cutting a dovetail with a mill or file. First, it is easier and faster, and second, you have material to tap down onto the sight to tighten it, if if gets loose.
2) Tap the rear sight in the direction you want to move your group. Cut the sighting slot/"V" is always dead centre in the sight.
3) I finish the rifle completely before taking it to the range for testing and sighting in. Note that even though you have zeroed the sights, it may not shoot the same for the client. We all see the sights a little differently. Years of experience has taught me how high to make the sights so that very little filing is needed, on the rear sight at least. The front I intentionally make a little high so I can dress it down to bring the group into the "X" ring.
Here's an image of an original Jacob Kuntz rear sight in the MET in NYC, and one of the copy I made of it for my build. I still have no idea where the leaf sight is zero'd.
One last note - notice that the raised metal has been filed flush with the angle flat.
