Vaadin with Liferay 4

Hi,
We are planning to use the latest version of Vaadin with our future release based on Liferay 6,
Meanwhile I have been asked to make a demo of a Vaadin integration with our current platform that runs in Liferay 4.
Do you know if Vaadin (any version) supports Liferay 4?
Currently i am dealing with this exception:
Servlet.service() for servlet jsp threw exception java.lang.NoClassDefFoundError:com.liferay.portal.kernel.util.PropsUtil
This is fair since there is no PropsUtil class in my portal-service.jar, it's only in earlier versions of liferay.

Edit:
Managed to get it working by updating the portal-service.jar with the necessary classes, the rest is default JSR168 portlet config for Vaadin.

Right now the portlet is not instanceable.
While inspecting the generated source code i noticed the default widgetset does not load for the second portlet.
<script src="/VAADIN/widgetsets/com.vaadin.terminal.gwt.DefaultWidgetSet/com.vaadin.terminal.gwt.DefaultWidgetSet.nocache.js?1328616392661" language="javascript">
I copied the VAADIN folder inside ROOT/html and made the proper modifications in web.xml
<servlet-mapping>
<servlet-name>VaadinServlet</servlet-name>
<url-pattern>/VaadinApp/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>VaadinServlet</servlet-name>
<url-pattern>/VAADIN/*</url-pattern>
</servlet-mapping>
Also added:
# Path under which the VAADIN directory is located.
# (/html is the default so it is not needed.)
vaadin.resources.path=/html

# Portal-wide widget set
vaadin.widgetset=com.vaadin.terminal.gwt.DefaultWidgetSet
to my portal-ext.properties file

Multiple instances of the same Vaadin portlet on a single portal page are possible when using Portlet 2.0. In that case, you can e.g. on Liferay define your portlets as instanceable in liferay-portlet.xml. Portlet 1.0 Vaadin applications do not support running multiple instances of a portlet on a page.