Wong has a special count in Professional Blackjack for O/U 13 called "The Crush Count." He also recommends Arnold Snyder's article on the O/U 13 bet. You can find that article on his website. You pretty much only need to attack the sidebet with a good count system for it. You can use a reduced spread for a higher EV and lower variance.
However, being the only casino in the US with the O/U 13 side bet, they know how profitable it can be. They do not tolerate any significant action on it (or so I've been told).