Speculating on the mockup chess board program I used below I suggested that it couldn't change height or width. And then looking at the code so as to alter it to be able to, I started seeing function after function would work with the given height. In the end I ended up seeing it fed in by the PHP itself and took a couple guesses what it was called.
Makes an 8x10 chessboard.
The question at hand is given the promotion rule, when does the bias towards black's army of pawns even out with regard to the height of the board? At what height would an average player against an average player be more likely to win* with whites rather than blacks.
*winning defined as the capture of every piece.
Update: the answer appear to be greater than 8 and less than 12.