BCP for calling per-user SA after sa-exim

Hello,

	First off, sorry for the cross-post.  I'm not sure if this is better 
answered by the SA guys or the SA-exim guys so it's going to both.

I like the idea of using SA-exim because it's got some great features!  
I would also like to incorporate per-user SA for mail that makes it 
past SA-exim.  The question is what, if any, is the best common 
practice for doing this, or something like this.

The issues that I have found so far are that there doesn't seem to be a 
way to tell SA-exim to not tag messages below a certain spam-score so 
exim can pass it off to an SA transport via an SA router.  Can I delete 
the headers or something using an exim ACL?

I'v also tried looking at amavisd-new, but while it seems rather 
robust, it takes some of the features away that SA and SA-exim have, 
such as being able to add the spam score using _SCORE_ in the message 
header, being able to encapsulate the message inside a spam report that 
shows exactly why the message was tagged as spam, etc.

Anyone have any insight they can share?