Hello Bonnmac,
There are a few ways you could do this, one way would be to create the Self Signed SSL Certificate/Key from a User account (with owned ip) and then just copy that certificate overtop the ones currently being used by apache:
/etc/httpd/conf/ssl.crt/server.crt
/etc/httpd/conf/ssl.key/server.key
(the new ones will be created in:
/usr/local/directadmin/data/users/username/domains/domain.com.cert and .key)
OR
from ssh:
cd /etc/httpd/conf
make
and follow the directions given.
This will be a new feature added to DirectAdmin when time permits.
John