Getting more than a little nutty over this nut...
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But produced sort of a revelation:
Working backward from measured gaps and diameters (which are easier to measure accurately than the centers of round grooves or string tops), the string centers on my 2018 are at 0.405" +/- 1/100", which is probably about my MOE and also coincidentally is the difference in string radii, in a 45/65/85/105 set.
Given I measured with strings at tension, all were a couple thousandths thinner than nominal, too.
0.4" centers, on-center, would give me 0.125" edge gap on the G side, and 0.0975" on the E side. At the nut.
Keepin' it real, If I can cut the finished width slots with handtools accurate to +/- a hundredth placement, it'll be a pretty good day.