A "trick" that I have used several times with excellent results. Install the dowels in the wing, BUT DO NOT ROUND THEM OFF, leave them flat. Take a #2 pencil and heavily blacken the ends of the dowels (Old fashioned carbon paper also works VERY WELL), and put the wing in position and push forward to mark the location of the dowels on the fuselage. Then drill with the appropriate size drill. Then you can round the end of the dowels.