Democracy can be a bitch can't it. Based on other elections, you can in on year be dished up a pile of drongos, deadbeats and d1ckheads and in another election a dream team. The difficulty with a seven member board is that in a bad year you don't have the other 6 (in a 13 member board) picking up the slack. If we could asses the amount of work to be done divided by the effort reasonably provide by a good director. You would arrive at the size of a good board. Double that for the vagaries
of democracy and you have the unique size of a FAQ board. Too strong and they harass the CEO, too weak and the CEO becomes the puppet master.
Corporate boards work, not because of democracy, but through nepotism and patronage, where cliques has control over a large bundle of shares, usually trustee companies and superfunds associated with the current board and a swag of proxies controlled by the chair. Or in the case of NewsCorp by a division between A shares and nonvoting B shares.
But don't expect Corporate Boards to be pure and lilywhite as they are just as likely to be of the opinion that what is good for the company and board is good for the shareholders and staff.
One can tinker with the voting system all you like but the major game changer is not the size of the board or its mode of election but the degree of transparency about board activity and director and candidate quality.