You have to be carefull with overlapping NAT/PAT statements within your config. PIX accepts it and this is good, but the problems you will be getting is with the returning traffic (in most cases). You have to make sure that returning traffic is not translated.
Yes, you can have overlaps
Yes, it can cause sesious trouble
and Yes, it can also work with the proper configuration.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...