Over/Under13

I play BJ using Hi-Low count. Soon I will visit Europe, where often bj rules are way worst then in US, but over/under13 is a common side bet. Is there any way of beating this bet using Hi-Low or a similar system? Some websites claim so, and sell a "system" for $99. I�m not going to spend this kind of money on a system sold on the net, but it seems to make some sense. Can someone help me with that?