Using the domain mapping plugin when WP is not installed in / (DocumentRoot)

For a number of reasons that would probably complicate matters by delving into (they involve integrating WP with CodeIgniter), I would like to be able to domain map to sites where WordPress lives in /wordpress relative to DocumentRoot rather than /. I have a current scheme which works for me, but it would be nice to be able to create new WP sites through the WP GUI…

I know that this is difficult to work around, but before I give up on the WordPress 3.x MU features, I thought I’d check to see if anybody has gotten this to work for them – specifically WordPress living in /wordpress rather than /?