Multisite & UserDir issues

hi,

me and some other guys are just busy getting some fresh air to our departmental website, and so far drupal works perfectly! :)

now, our goal is to provide users with the possibilty to make use of the existing drupal installation.

1. i understand that you have to make sure that
   • a request for a user's site (say www.example.com/~user/) gets redirected to our drupal installation and
   • there is a folder/symlink in <drupal>/sites/example.com.~user.

   now, the thing doesn't work as expected. we have a UserDir in apache that makes www.example.com/~user/ point to <home_of_user>/public_html which in turn symlinks to <drupal>. one gets to www.example.com/~user/ without any problems, but it is impossible to access any site below it, such as www.example.com/~username/user for example: the only thing you get is 404's of www.example.com. hm...

2. another, unrelated question is whether it is actually possible for a user to have non-drupal subsites. if john doe has a full-blown drupal installation in his public_html, he could easily create symlinks to, for example, his websvn installation by doing
   cd public_html
ln -s path-to-websvn websvn

   it doesn't seem so obviously possible with the multisite thing going on.

-- any hints, here?

cheers,
nico