Using an N box transition was the method that I was trying before, and having no luck with. It could be that through that practise, I learned that one aspect (hard 2xs, gentle 4s) and that prepared me to be more ready for the 423 method.
It reminds me of and saying in chemistry: Which quantum chemistry textbook is the best to learn from? The third one you read.
by Mike Moore, in response to this post 2015-08-12 13:24:55