You are getting serious!
The leach cringle is normally slightly higher than the luff cringle to lift the boom slightly – keeps it off heads.
I found even with an old and baggy sail a second reef gave a really flat and low power shape, so don’t have the second reef too deep. The usual is about 3 feet, but I have more than thet on my first reef – just over a metre I think. You need to start the other end really and measure down the mast from round about a foot above the shroud band to the boom. That is how long you want your luff when the second reef is in. Much lower and the sail will be too small.