Best bet is to call Dave at IMPROS and tell him your mods and what type of riding you do and he'll give you an exact pitch that would suite your riding style.
His reccommendations for my SXR with a stock motor for ocean riding was 13/17 5mm cutback (repitched stock swirl style impeller)
His recommendaiton for my SJ mild limited setup for ocean riding was either 13/17 3mm cutback or 13/16 3mm cutback
www.impros.com