I see you have completed your pipe fence and its a real beauty. Very pleasing to the eye. If you ever build another one I might suggest laying out the fence directly on the curved driveway. I would simply measure and chalk the center of the driveway and layout the pipe on top of my chalk marks. Weld the vertical pipe posts and drag the fence (in sections) over to the correct distance from the driveway. I would then drill my holes using the bottom of my vertical pipes as my guide. Im always a "Johnny come lately" and seem to have my ideas after the project is completed but maybe in the future this might give you some additional ideas. Again great project and beautiful job.