Boeing count appears to be pretty complex, in a double three fashion. I use this count because I do not believe in expanding diagonals. They usually fail or lead you astray from the real count.
The first of the double three correction is a 5-3-5 zigzag then followed by a 3-3-5 running flat, after this, I am expecting a 5-3-5 zigzag once again, started with a leading diagonal for the A wave.
I usually do not count double three corrections, but BA is the first I do not see another decent way to count it. Unless you allow expanding diagonals.