Tom Curren's bottom turn technique?

I've always loved this photo of Tom Curren's bottom turn:
What techniques is he using to perform this powerful, large-radius carve? His weighting looks somewhat unusual -- his rear foot is well in front of the fins, at least a foot but maybe two, and it looks like his weight is more on the front foot than many photos of other surfers doing a bottom turn on big waves. Anything else specific? And how would one use these observations to practice better bottom turns?
What do you think are the features of his board? What would lead to a board that is effective for making big, powerful, large-radius carves like this? It appears quite long, perhaps not really a short board, maybe even a semi-gun. Do you think it is very thin or not so much, low or high volume, rails of a particular type etc etc?
Thanks everyone!
What techniques is he using to perform this powerful, large-radius carve? His weighting looks somewhat unusual -- his rear foot is well in front of the fins, at least a foot but maybe two, and it looks like his weight is more on the front foot than many photos of other surfers doing a bottom turn on big waves. Anything else specific? And how would one use these observations to practice better bottom turns?
What do you think are the features of his board? What would lead to a board that is effective for making big, powerful, large-radius carves like this? It appears quite long, perhaps not really a short board, maybe even a semi-gun. Do you think it is very thin or not so much, low or high volume, rails of a particular type etc etc?
Thanks everyone!