hi ScottB.
I don't recommend rewriting rules changing the depth of the path.
If you want it anyway, try nobunobu's way.
http://www.kowa.org/modules/yybbs/viewbbs.php?bbs_id=4&serial=2164Though this post was written in Japanese, you have to read just "codes".
The original idea:
http://xoops.peak.ne.jp/md/news/index.php?page=article&storyid=54