iptables and openvpn bridge

I run openvpn on a linux (FC7) box with an ethernet bridge. As specified at
http://openvpn.net/bridge.html
I set iptables thus:
iptables -A INPUT -i tap0 -j ACCEPT iptables -A INPUT -i br0 -j ACCEPT iptables -A FORWARD -i br0 -j ACCEPT
Now it works, but this opens up much more on the host machine than I want. But I do not understand the paths so that I can know how to add additional restriction.

Can someone direct me to further relevant documentation?

Thanks,
Mike.