Well not quite opening up the back, it's more opening up the side. Creating more room for the knuckle, while keeping the back-to-front as tight as you like, with tape in the front.
Flicking your thumb back, or basically trying to maintain a "thumbs up" throughout the release, is essential as well. That is one of the secrets to being able to use forward pitch effectively. The 3/8 forward is by no means too much, but you have to be able to use it correctly.
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The Right Approach Pro Shop, Charlotte, NC