whopper plopper 90 hooks

I know theres an old thread on this with a few responses. Im picking up some gamakastu ewg short shank hooks and am wondering what size to put on the front. size 4 or 6? I heard some people use size 4 and others use size 6. what size hook is closest to size as the stock hook? I would like the exact size as the stock hook. im pretty sure the stock hook is a 4 but a size 4 for one company isnt always the same as a size 4 from another. thanks