One of the problems is the outboard terminous of the spindle, as alluded to, they crank will only fit so far, as the wedge will allow it to go, the point at which the mfg. cuts it off can make a difference, even Campagnolo spindles vary by a millimeter during a given era, its the taper placement in relationship to the bearing contact point that drives the crank placement. The taper and placement are hard to measure without some set ups to assist, in my tool box long stolen I had a device that helped, think of a hinge basically with a ground inside face set, I recall it was 6 inches long or so, it provided a long enough leg to measure the taper through trig, measuring the short section of taper a spindle has without a reference plane is mind numbing.