In stockmaking for doubles, what is the best method for drilling the holes for the screws that go between the top tang and the trigger plate. I believe these would be the breech screw (the big important one under the top lever of top lever guns) and the grip or tang screw, correct me if I have the terminology wrong, I hope you have the picture. How does one go about making dead sure of alignment before drilling? I take it these holes must be a fairly tight fit on the shank of the screws (pins) too. How close a fit is good enough?

Thanks,
Tony