how to share a cache between two squid processes

Ok, here's what I'm ultimately trying to do:
I'd like to have one cache that is a straight cache, and the other cache
that'd be an add filtering, anonymizing cache.

Ideally I'd like to have squid answer two port numbers 3128 and 3129, and
use a different director program depending on which port was selected.
If I could have each squid use a different config file altogether, it'd be
even better (one could use fake_user_agent)

What I've looked at:
- Running two completely independant squid instances That's bad, as that
  even if I set ICP between the two, they'd still be duplicating stuff in
  memory and on disk, so it doubles hardware requirements
- redirectors like squidguard can let me apply the redirect rules
  differently depending on the from IP or user ident, but that would require
  that I maintain the list of which user gets the normal cache and which one
  gets the filtering cahe, and the users would have to ask every time they
  want to switch.
- Use an external app like junkbuster and have it request its pages from
  squid

I am currently leaning toward the third option.
Anyone has a better suggestion?

Thanks,
Marc

-- 
Microsoft is to software what McDonalds is to gourmet cooking
 
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