I don't know the reason they would advise that since when I dynoed my bike with 160 main and 42 pilot way back when I first started setting my bike up it was so lean it didn't even register on the graph until the slide opened. Then I was just about perfect. So up the pilot lower the main some and I am really close and I run a 48 pilot and 155 main. Gutted stock pipes with reducer cone still in place and pods.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!