Multisite htaccess on localhost with WP as an SVN external?

I’ve mimicked Otto’s setup here: http://ottopress.com/2011/creating-a-wordpress-site-using-svn/ and my brief example is below.

That tutorial is specific to a single site install, and specifies a single domain. How can I customize the htaccess below to be suitable for multisite? Note that the multisite htaccess WordPress provides doesn’t work because the wp directory is custom.

Directory Setup

• C:wampwwwmy_site – Site root
• C:wampwwwmy_sitewp-config.php – Config
• C:wampwwwmy_sitewp – WordPress as an SVN external
• C:wampwwwmy_sitecustom-content – Custom content dir

Apache Setup

<VirtualHost 127.0.0.1>
    ServerName example.com
    DocumentRoot "C:/wamp/www/my_site"
    ServerAdmin me@example.com

    <Directory C:/wamp/www/my_site>
        Order Allow,Deny
        Allow from all
    </Directory>
</VirtualHost>

htaccess

Options -Indexes
RewriteEngine on
RewriteCond %{HTTP_HOST} ^(www.)?example.com$
RewriteCond %{REQUEST_URI} !^/wp/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /wp/$1
RewriteCond %{HTTP_HOST} ^(www.)?example.com$
RewriteRule ^(/)?$ wp/index.php [L]