Specify non-default path to spamassassin rules?

Hi,

I'm trying to configure a second instance of amavisd to run on a different
port that has a completely different set of rules other than the default
/usr/share/spamassassin and /var/lib/spamassassin. How can I do this?

I already have postfix running on multiple IPs - I'd like to have amavisd
run on one port for one of the IPs and another port for the other IP.

It looks like perhaps LOCAL_STATE_DIR and LOCAL_RULES_DIR can be redefined
from the defaults?

The reason for this is that I have one domain that wants one set of rules,
and a number of other domains who only need/want very specific rules to be
used.

Thanks,
Alex