default policy will be ACCEPT, for tests period at least. As I can understand - your sample firewall script not from Oleg's 1.9.2.7-10 (which based on 2.4 kernel too), isn't it?
Bad news - kernel 2.4.X don't support ipv6 connection tracking(ip6_conntrack) at all. And nobody done backport from 2.6 line
Also, I can't find ipv6 TCPMSS module for 2.4 ...
About radvd - many software developers increase versions too rapid, without real core functionality change, especially commercial software. So, I don't want to repair new bugs in new version due to incompatibility with our obsolete 2.4 kernel.