I've ended up with copies of the Jasey Jay Anderson board & plate setup instructions.
They make intriguing reading, for a number of reasons. (JJA's preferred stance for a start, and he's 177cm tall)
Some might argue with his analysis of what happens when you adjust plate mounting points, others might debate what "stiffness" means (in terms of snowboards, you've got filthy minds!). Personally, if you take a child's ruler, hold one end down on a firm surface, and bend and release the other end the fact that it makes a different sound when the protruding length is shorter is not because the ruler has become more stiff.
If anyone has photos of the underside of a JJA plate, or any evidence that the mechanism limits the amount to which a board can flex underneath it I'd be interested to see it.
Board-Setup.pdf
Interface-Guidelines..pdf