Hi Robert,
If you need real blank line, no choice, you need to use containers to manage the disposition.
For instance:
<container type="hpaned">
Use padding-top attribute (or padding-bottom) to add pixels above (below) the container.
Other attributes are described in the JSAPI documentation.
Some other attributes are not described in the documentation and you can find out in the forms code...
Regards.
J-Serge