I think changing thumb pitches is more about the flexibility of your hand and how the ball feels.  I changed my thumb pitch when I changed my finger pitch, but my hand is very pliable and it would not have been necessary.  Some people might have trouble losing the ball with reverse in the thumb and forward in the fingers.  I don't think it would be necessary to go all the way to forward pitch, but maybe going to 0 would be a good compromise.