Andy,

Not sure if you already know or not but if you want native IPv6 over PPPoE support then you have to use 5.0rc. It was an unsupported/undocumented feature in early versions of 4.x but they intentionally disabled it at some point to fix a bug. It got reenabled along with official support in 5.0 which is still in "release candidate" stage which seems to get a lot of new features...

I've been using 5.0rc for months now and I've not had any issues with it at all at least with the features I'm using.