For me the goal is to be happy with the quality of the work I do. I strive for excellence but get less. If I stop agonizing over my work with in a day or so then the quality of work is ultimately expectable. The side skin curves inward at the forward end at the firewall weldmont and I really wanted to drill perpendicular to the skin surface. I have discovered that I have a good eye for vertical and horizontal but not in between.
So, as seen in image 1 I wrapped a light piece of balsa wood with double sided sticky tape and stuck the stick perpendicular to the skin next to each hole I was about to drill. Then I used a small square to square up the drill chuck with the stick. I was impressed in that I could not guess the angle without the stick very well. I tested each hole and made sure a universal rivet set flush with the skin. They all did. I’m happy.