So I'm sort of slogging through my first build with a kit from CB Gitty and as some of you are aware totally trashed my first neck due to ignorance on my part ... but I learned something. Yesterday I cut the notches into the cigar box and did an ace job on that - nice tight fit - nice and square. But still sort of stumbling along reading the little booklet from Gitty and of course reading posts here and watching many videos. But was still bothered by mysteries around getting the action close to right or at least fixable. 

I then came across this video about CBG string action

https://www.youtube.com/watch?v=WZ3F7-aXMiw

He rambles a bit here and there but the key piece of info is to have your fingerboard ABOVE the top of your cigar box. This is crucial so that your bridge can be high enough to create a decent break angle to back where the strings attach to the end of the neck or the guitar body without needing a bridge so high your action is out of whack. And indeed if I look at the 3 guitars I have: a Strat - an Ibanez - and a Martin all have the fingerboard at least a 1/4" above the body of the guitar. I think this is a pretty huge decision that needs to be made early on in your design .... by sheer luck I cut my slots in the box using only the neck and not the neck and fingerboard. So indeed my finger board will be 1/4" over the top of the box. Yes I have seen many discussions here on and around this topic but this video for me nailed it. Hope it helps someone else.

A related issue is neck angle which he also discuses and I could see if you did have a neck flush with the top of the box adding some neck angle could help to create some string break angle at the bridge. I may add a very slight angle to this build.