It started out as the Patrick Girard layout, as Rick Benoit first used it for him when he was on tour a few years ago.
The pin is placed roughly 5 1/2-6" from the negative axis point. The reason why it is placed below the thumb is to allow the flare to properly migrate around the thumb, using the lower bow tie, as opposed to the upper bow tie by the fingers. Reason for this is that the flare, having the pin based off the NAP, it will invert the flare (or flare backwards), so it is necessary to manage the flare similar to a full roller layout.
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Formerly BrunsRico