Hello,
You can either modify the virtualhost templates, or use the custom httpd.conf feature to insert httpd.conf snippets into the virtualhost.
1) cd /usr/local/directadmin/data/templates
cp virtual_host* custom
cd custom
#edit the 4 virtual hosts as needed.
echo "action=rewrite&value=httpd" >> /usr/local/directadmin/data/task.queue
and/or
2) Admin Panel -> Admin Settings -> Customize Httpd Configurations -> domain.com
Then add the httpd.conf code into the text area. The code you enter will be inserted into the |CUSTOM| token in the virtualhost templates that are mentioned in 1) (above). (So do not past a whole virtualhost, just the few lines you want to insert).
John