I believe that all of the custom lugs that I have seen looked like they had had their front and back surfaces ground on a surface grinder. As far as needing to have a controlled environment to measure to ten thousandths goes, I believe that that applies if and absolute dimension is what is being sought, but if you are measuring on two or more place on the same piece to see if the measurements are the same, then all you are looking for is any difference, not the absolute measurement. For instance if a part measured .2504 at one point and .2500 at another, if the temperature at which it was measured was not standard, then the absolute value of both might be off, but the fact that they were different, and the relative magnitude would still be useful information. As far as technique becoming more of an issue, when working to ten thousandths, I agree completely. A friend, who was a long time bullet maker, told me that he would not look at the micrometer's reading until after he had the mic. set, so that his technique would not be influenced by the measurement that he wanted. Also, I have found that dragging a piece through the mic. sometimes give me a better feel, particularly when measuring things that are easily deformed.