Nucejoe- if the hole drifts you can see it either with a measuring microscope or jig borer or in a faceplate, centering on the corresponding hole and comparing. All require a certain amount of equipment. Ckelly, your method of measuring bores is an established one though not ultra accurate. If you want I'll do your bushing and try to get some decent pics of the process just for educational purposes, it's a pretty quick job but you'd have to ship to Switzerland..