For the many of you that are not gunsmiths or machinists, I just updated an article on measuring dovetail slot dimensions. It discusses four methods to determine the dovetail dimension, some more accurate and easier than others. The link to the article is
http://www.texas-mac.com/Measuring_Dovetail_Slot_Dimensions.html

Wayne

If in doubt or concerned, always go a little large. Much easier to file them down to size as opposed to having to add material.