Those inlays are fantastic! Do you have to fiddle with the design much to get them to fit together so well or have you got it pretty well down at the modeling stage?
Making the inlay 0.2mm smaller than the outer piece seems to be the go to number. Some fit together a little tighter than others and you got to watch things like the number 8, the outer needs to shrink 0.2mm while the inner parts of the 8 needs to get larger by 0.2mm. I also had to trim off the flashing on some parts, (the squish out from the first layer). But not really a whole lot of post work.
Some things are meant to be closed. Your mind isn't one of them.