Looking really good.
I read somewhere that the strings should sit with half inside the nut groove and half above. (cannot remember where I read this though!) I generally start with that positioning.
I also take into account how close the string is to the frets to avoid buzzing. If you need to cut down further into the nut you can always sand part of the top off if it is needed but that is personal preference and depends on how you play.
As Simon said the height you set the string depends on your playing style, so the best approach is to small steps when cutting down into the nut.